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| Meta Title | Hurricane Irma | Path, Damage, Category, Wind Speed, Death Toll, & Recovery | Britannica |
| Meta Description | Hurricane Irma was a powerful category 5 Atlantic Ocean hurricane in 2017. Irma caused significant damage and deaths across the Caribbean and Florida, with sustained winds of 185 miles (298 km) per hour. |
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| Boilerpipe Text | Top Questions
What is a natural disaster?
What are some common types of natural disasters?
How do natural disasters happen?
What effects can natural disasters have on people and the environment?
How do people prepare for and respond to natural disasters?
How can communities reduce the damage caused by natural disasters?
natural disaster
, any calamitous occurrence generated by the effects of natural, rather than human-driven, phenomena that produces great loss of
human
life
or destruction of the natural
environment
, private property, or public
infrastructure
. A natural
disaster
may be caused by
weather
and
climate
events or by
earthquakes
,
landslides
, and other occurrences that originate at
Earth
’s surface or within the
planet
itself. No spot on Earth is immune from a natural disaster; however, certain types of disasters are often limited to or occur more frequently in specific geographic regions.
Types
Weather- and climate-driven natural disasters include
flooding
caused by heavy
rains
associated with hurricanes and typhoons (
tropical cyclones
) and other intense storms;
drought
,
famine
, and
wildfires
brought on by
heat waves
and shifts in
precipitation
patterns;
wind
-generated devastation caused by tropical cyclones,
tornadoes
,
derechos
, and other
windstorms
; and damage and loss of life caused by
blizzards
and heavy snowfalls. Earth-driven natural disasters include large
volcanic eruptions
(which produce
lava
flows, explosions,
toxic
gas clouds, ash falls, and
pyroclastic flows
that damage populated areas) and strong earthquakes (which result from the sudden fracturing of Earth’s
crust
) powerful enough to damage or destroy built-up areas near their origin points.
landslide
A landslide is a movement downslope of a mass of rock, debris, earth, or soil (soil being a mixture of earth and debris).Â
Some phenomena that produce natural disasters may be caused by a combination of several different forces. For example, landslides (the movement of large masses of
rock
, debris, and
soil
downslope) may be caused by rains that saturate the soil on an unstable slope, or they may be triggered by earthquakes. In a similar manner, the buildup of
snow
on
mountain
slopes increases the risks of localized
avalanches
.
Tsunamis
, catastrophic ocean
waves
that can rise as high as 30 metres (about 100 feet) above normal
sea level
, are produced by submarine earthquakes, underwater or coastal landslides, volcanic eruptions, or
meteor
or
comet
impacts. The largest tsunamis are fast-moving waves that can travel across oceans to wreak
havoc
in coastal areas separated thousands of kilometres from one another.
Frequency and disaster patterns
Certain types of natural disasters are more likely to occur in specific geographic regions, and in some places these events occur with seasonal regularity, as in the spring
tornado
season in the
United States
or the summer-and-fall
hurricane
season in the
Atlantic Ocean
,
Caribbean Sea
, and the
Gulf of Mexico
. Earthquakes and volcanic eruptions are most frequent near
tectonic plate
boundaries, and an especially active boundary exists between the Indo-Australian and Eurasian plates.
The
World Meteorological Organization
(WMO)—a
United Nations
(UN) agency that monitors Earth’s land,
water
, and
atmosphere
—reported in 2021 that the number of natural disasters per decade showed a fivefold increase from 1979 to 2019, and
data
collected in the EM-DAT, an international disaster database maintained by the Center for Research on the Epidemiology of Disasters, Brussels, indicate that more than 300 disasters have been tallied each year since 1998. Though many natural disasters are neither preventable nor largely predictable, the WMO report notes that
global warming
—an increasingly human-driven phenomenon generated by the emission of
greenhouse gases
, specifically those released by the
combustion
of
fossil fuels
—is increasing the frequency of weather- and climate-related natural disasters, such as droughts, heat waves, increasingly intense hurricanes, and flooding due to sea-level rise. Warmer temperatures are causing more extreme weather events by delivering more precipitation to some areas—which may be unused to receiving heavy rains and snows, increasing flooding risk—while delivering less to other areas that rely on it, increasing
drought
risk. In addition, reliable sources of rainfall, such as the
South Asian monsoon
, on which agriculture of the
Indian subcontinent
has long depended, are becoming less predictable, and rain events have become more violent and dangerous, damaging crops and producing more intense flooding. This change has subjected some areas under the monsoon’s influence to extended drought conditions, whereas other areas receive too much rainfall, a pattern that scientists predict will worsen in the 21st century.
Damage and deaths
Superdome
Aerial views of downtown New Orleans, Louisiana, with the Superdome in the foreground: (left) on August 30, 2005, a day after Hurricane Katrina struck the city, and (right) again some 10 years later on July 29, 2015.
The costs of individual natural disasters frequently reach the tens of billions of dollars. Such costs may be associated with damage to crops, buildings, and
infrastructure
that occurs annually in areas prone to tropical cyclone activity or heavy seasonal rains, with some events, such as the
Pakistan
floods of 2022 and
Hurricane Katrina
(which struck the southern United States in 2005), costing more than $30 billion and $186 billion, respectively. Similarly, costs associated with earthquakes, which occur less regularly, can be high (such as
China
’s
Sichuan earthquake of 2008
and
Japan
’s
KĹŤbe earthquake of 1995
, which incurred costs estimated at more than $86 billion and more than $100 billion, respectively).
The number of
deaths
from natural disasters also varies by location and the intensity of the event; however, the overall
trend
points to a decline from several hundreds of thousands of deaths annually during the first half of the 20th century to roughly 45,000 deaths globally each year. The number of deaths also varies widely from year to year, with smaller natural disasters (or natural disasters occurring in areas far from human settlement) killing few and shockingly large disasters producing truly massive losses of life. Some of the most notable catastrophic disasters in history include the
Indian Ocean tsunami of 2004
(which killed more than 225,000 people), the
Tangshan earthquake of 1976
(which resulted in more than 242,000 deaths), the
2010 Haiti earthquake
(which by some estimates may have killed at least 300,000 people), and China’s
Shaanxi province earthquake of 1556
(which killed more than 800,000 people).
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Although deaths from natural disasters have decreased overall, people in lower-income countries often suffer disproportionately, because these locations have fewer resources and thus greater vulnerability to the elements and to
food insecurity
. In contrast, highly developed countries have better infrastructure (for communications, evacuation procedures, the movement of resources, and the delivery of medical services). In addition, high-income countries can
implement
policies that limit construction in flood-prone areas or
mandate
the construction of more earthquake-resistant homes, office buildings, and other structures, thereby reducing the risk of
crushing injury
and death stemming from building collapses. Consequently, relatively few people die from earthquakes in
California
, a location well-known for its strong building codes with respect to withstanding earthquakes, compared with places such as
Iran
and Pakistan, where building codes are either less stringent or whose codes frequently go unenforced.
Disaster warning systems
Doppler radar
Doppler radars, such as this one operated by the U.S. National Weather Service at New Underwood, South Dakota, extract the Doppler frequency shift of the echo produced by a moving target by noting how much the frequency of the received signal differs from the frequency of the signal that was transmitted.
Advances in
weather forecasting
and advances in land-based seismic sensors and sensors placed aboard
satellites
, aircraft, and stationary
buoys
floating in the world’s
oceans
have led to the development of various kinds of early warning systems. In some cases, these systems are capable of predicting or accurately classifying the strength of the physical forces that generate natural disasters before they cause damage. The perhaps most
widespread
and best known of these systems are those used by national
weather bureaus
that classify, track, and predict various weather events and issue bulletins about storms and other weather and climate phenomena affecting their land areas and sea zones. National weather bureaus are often made up of a network of numerous local offices spread across a country that gauge local weather conditions several times per day. Data collected by these offices can be used to develop weather models that help to predict the strength of a
storm
, as well as its location, days in advance of its arrival in a local area.
In addition, specialized units within national governments—such as the China Earthquake Administration, the Japan Meteorological Agency, the United Kingdom’s Met Office, India’s National Center of Seismology, the U.S.
National Oceanic and Atmospheric Administration
, and the U.S. Geological Survey—monitor specific physical forces capable of causing the most damaging and deadly natural disasters (that is, earthquakes, tsunamis,
droughts
, flooding, and winds driven by tornadoes and tropical cyclones). Many of these organizations within specific countries cooperate with their counterparts in others or assist international organizations, such as the WMO and the International Tsunami Information Center, to issue warnings, develop international safety standards, and assess the risks associated with forces that affect several countries or the planet as a whole. Some early warning systems even look beyond Earth’s atmosphere; the near-Earth objects system operated by the
European Space Agency
and the Scout and Sentry impact hazard systems run by
NASA
in the United States are a few of several systems designed to detect, track, and predict the risk associated with
asteroids
, comets, and other extraterrestrial objects capable of striking Earth. |
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[Hurricane Irma](https://www.britannica.com/event/Hurricane-Irma-2017)
- [Introduction & Top Questions](https://www.britannica.com/event/Hurricane-Irma-2017)
- [Development](https://www.britannica.com/event/Hurricane-Irma-2017#ref433919)
- [Damage](https://www.britannica.com/event/Hurricane-Irma-2017#ref433920)
- [Aftermath](https://www.britannica.com/event/Hurricane-Irma-2017#ref433921)
[References & Edit History](https://www.britannica.com/event/Hurricane-Irma-2017/additional-info) [Quick Facts & Related Topics](https://www.britannica.com/facts/Hurricane-Irma-2017)
[Images & Videos](https://www.britannica.com/event/Hurricane-Irma-2017/images-videos)
[](https://cdn.britannica.com/30/276330-050-A839E311/Activity-Graph-From-National-Hurricane-Center-From-September-10-2017-Shows-5-Day-Forecast-Track-Of-Hurricane-Irma.jpg) [](https://cdn.britannica.com/34/276334-050-D73C7F8E/Activity-Graph-From-NHC-CPHC-From-September-2017-Shows-Hurricane-Irma-Wind-Force-For-120-Hours.jpg) [](https://cdn.britannica.com/41/273741-050-D20648DA/saffir-simpson-hurricane-wind-scale-storm-surge-cyclone.jpg)
[](https://www.britannica.com/video/hurricanes-typhoons-rules-names-World-Meteorological-Organization/-238839)
[](https://cdn.britannica.com/25/276225-050-F86E80D7/Hurricane-Irma-2017-Caused-Destruction-Flooding-Across-Caribbean-Prompting-Evacuation-Operations.jpg) [](https://cdn.britannica.com/05/274305-050-B35C08CD/hurricanes-by-numbers-named-facts.jpg) [](https://cdn.britannica.com/52/264452-050-B7C72142/Storm-surge-illustration-Hurricane-Katrina-Ian-Irma.jpg)
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[Graphic showing Hurricane Irma's five-day forecast and warning](https://cdn.britannica.com/30/276330-050-A839E311/Activity-Graph-From-National-Hurricane-Center-From-September-10-2017-Shows-5-Day-Forecast-Track-Of-Hurricane-Irma.jpg) The cone represents the probable track of the center of the storm.
(more)
# Hurricane Irma
Atlantic Ocean storm \[2017\]
Homework Help
Written by
[Michele Metych Michele Metych is the lead editor for *Today in History* at *Encyclopædia Britannica*.](https://www.britannica.com/editor/Michele-Metych/9760897)
Michele Metych
Fact-checked by
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[History](https://www.britannica.com/event/Hurricane-Irma-2017/additional-info#history)
 Britannica AI
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Top Questions
### What was the wind speed of Hurricane Irma?
Hurricane Irma sustained [wind](https://www.britannica.com/science/wind) speeds of 185 miles (298 km) per hour.
### How long did Hurricane Irma maintain its category 5 status?
Hurricane Irma spent a total of 78 hours as a category 5 [storm](https://www.britannica.com/science/storm).
### What was the estimated damage cost and death toll from Hurricane Irma?
Damage from Hurricane Irma was estimated to cost about \$90 billion. At least 129 people lost their lives because of the direct or indirect effects of the [hurricane](https://www.britannica.com/science/hurricane-weather).
**Hurricane Irma**, one of the longest-lasting category 5 [hurricanes](https://www.britannica.com/science/hurricane-weather) on record that hit the [Caribbean](https://www.britannica.com/place/West-Indies-island-group-Atlantic-Ocean) and the southern [United States](https://www.britannica.com/place/United-States) in 2017. With [sustained](https://www.britannica.com/dictionary/sustained) [wind](https://www.britannica.com/science/wind) speeds of 185 miles (298 km) per hour, Irma was the strongest [tropical cyclone](https://www.britannica.com/science/tropical-cyclone) to strike the Caribbean at the time of landfall and the strongest hurricane recorded over the open [Atlantic Ocean](https://www.britannica.com/place/Atlantic-Ocean) as of 2025. Between August 30 and September 12, Irma made landfall seven times across the Caribbean and [Florida](https://www.britannica.com/place/Florida), causing widespread destruction. The effects of Irma were so great that the World Meteorological Organization retired the name in 2017.
Four of Irma’s landfalls were at category 5 strength, with wind speeds of more than 157 miles (253 km) per hour. It spent a total of 78 hours as a category 5 [storm](https://www.britannica.com/science/storm), tying the 1932 Cuba Hurricane of Santa Cruz del Sur for the longest [duration](https://www.britannica.com/dictionary/duration) in that category on record. Irma maintained its top wind speed of 185 miles (298 km) per hour for 37 hours, longer than any other tropical cyclone in history. At its most intense, Irma’s [barometric pressure](https://www.britannica.com/science/atmospheric-pressure) dropped to 914 millibars, an almost 10 percent decrease, creating an atmospheric vacuum. Irma’s core at its peak was relatively compact, with hurricane-force winds extending just 15 nautical miles (17 miles \[28 km\]) from the center.
## Development
[](https://cdn.britannica.com/34/276334-050-D73C7F8E/Activity-Graph-From-NHC-CPHC-From-September-2017-Shows-Hurricane-Irma-Wind-Force-For-120-Hours.jpg)
[Probability of hurricane-force winds during Hurricane Irma](https://cdn.britannica.com/34/276334-050-D73C7F8E/Activity-Graph-From-NHC-CPHC-From-September-2017-Shows-Hurricane-Irma-Wind-Force-For-120-Hours.jpg)A graphic showing the likelihood of winds reaching or exceeding hurricane force (which is 74 miles \[about 120 km\] per hour) at specific locations along the hurricane's path over a given time period.
(more)
Irma originated as a tropical wave (an atmospheric trough or low air-pressure area) off the west coast of [Africa](https://www.britannica.com/place/Africa) on August 27. Conditions were favorable for storm development, with warmer-than-average seas and light winds in the upper [atmosphere](https://www.britannica.com/science/atmosphere). By the time the wave reached the [Cabo Verde Islands](https://www.britannica.com/place/Cabo-Verde) on August 30, it had strengthened to a tropical depression and became a [tropical storm](https://www.britannica.com/science/tropical-storm) just six hours later. Irma intensified quickly because of low [wind shear](https://www.britannica.com/science/wind-shear) and warm seas, reaching hurricane status 30 hours later on August 31. At this point Irma was still located over the eastern Atlantic, 400 nautical miles (460 miles \[741 km\]) west of the Cabo Verde Islands.
[](https://cdn.britannica.com/41/273741-050-D20648DA/saffir-simpson-hurricane-wind-scale-storm-surge-cyclone.jpg)
[Saffir-Simpson hurricane scale](https://cdn.britannica.com/41/273741-050-D20648DA/saffir-simpson-hurricane-wind-scale-storm-surge-cyclone.jpg)The scale is used to classify tropical cyclones occurring in the Atlantic Ocean and northern Pacific Ocean basins east of the International Date Line.
(more)
Irma reached major hurricane status, with a wind speed of at least 100 knots (115 miles \[185 km\] per hour), on September 1—an increase of 70 knots (81 miles \[130 km\] per hour) in less than 48 hours. Such a rate of intensification is rarely seen in Atlantic tropical cyclones; only 1 in 30 generally [accelerate](https://www.britannica.com/dictionary/accelerate) at such a rate, according to the U.S. National Hurricane Center.
Irma fluctuated between a category 2 and category 3 hurricane until September 4, likely because of an influx of dry air and [eyewall](https://www.britannica.com/science/tropical-cyclone#ref247918) replacement cycles. (This is a process in which an outer eyewall, which is a broad ring of thunderstorms, contracts inward, cuts off inflow to the original smaller eyewall surrounding the [eye of the storm](https://www.britannica.com/science/tropical-cyclone#ref247917), and ultimately replaces it.) A high-pressure system to its north caused Irma to turn west-southwestward, toward the [Leeward Islands](https://www.britannica.com/place/Leeward-Islands). It intensified to 155 knots (178 miles \[287 km\] per hour) on September 5, when it was just 70 miles (113 km) from [Barbuda](https://www.britannica.com/place/Antigua-and-Barbuda).
Irma made its first landfall as a category 5 storm on Barbuda at 1:45 am local time on September 6. [Storm surge](https://www.britannica.com/science/tropical-cyclone/The-storm-surge#ref247928) was significant, with estimates suggesting about 8 feet (2 meters) of water. Irma continued on to [Saint Martin](https://www.britannica.com/place/Saint-Martin-island-West-Indies) and [Virgin Gorda](https://www.britannica.com/place/Virgin-Gorda-Island) that same day, with similar intensity, before weakening slightly as it approached [Puerto Rico](https://www.britannica.com/place/Puerto-Rico). Although Irma did not make landfall in Puerto Rico, it left drenching rain—10–15 inches (25–38 cm)—and the island was mostly without electricity and water for days.
The storm then passed over the [Turks and Caicos](https://www.britannica.com/place/Turks-and-Caicos-Islands) and the [Bahamas](https://www.britannica.com/place/The-Bahamas), making landfall on the latter as a category 4 hurricane at 1:00 am local time on September 8, thereby ending a 60-hour [spree](https://www.britannica.com/dictionary/spree) as a category 5 storm.
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About 18 hours later Irma restrengthened into a category 5 hurricane before making its fifth landfall in northern [Cuba](https://www.britannica.com/place/Cuba) late on September 8, driving waves and seawater a half mile inland. Irma then tracked along Cuba, and the land interaction caused it to weaken to a category 2 about 15 hours later.
Once Irma’s core reached the warm [Straits of Florida](https://www.britannica.com/place/Straits-of-Florida), it intensified again, becoming a category 4 storm on September 10, about 55 nautical miles (63 miles \[102 km\]) from [Key West](https://www.britannica.com/place/Key-West), before making its sixth landfall near Cudjoe Key about 9:00 am local time. High-water marks near Big Pine Key suggested a storm surge of about 8 feet (2 meters). Flooding in [Miami](https://www.britannica.com/place/Miami-Florida) was driven by a combination of heavy rain, urban [runoff](https://www.britannica.com/science/runoff), and seawater intrusion into the city’s sewer systems.
[](https://www.britannica.com/video/hurricanes-typhoons-rules-names-World-Meteorological-Organization/-238839)
How are hurricanes and typhoons named?During World War II, U.S. Navy and Army meteorologists began using their wives' and girlfriends' names for storms.
(more)
[See all videos for this article](https://www.britannica.com/event/Hurricane-Irma-2017/images-videos)
Irma then dropped to a category 3 before making its final landfall near Marco Island a few hours later. It subsequently weakened to category 1 and widened before passing over much of central Florida, including [Tampa](https://www.britannica.com/place/Tampa) and [Orlando](https://www.britannica.com/place/Orlando-Florida), with a wind field of 360 nautical miles (414 miles \[667 km\]) from the hurricane center. [Everglades National Park](https://www.britannica.com/place/Everglades-National-Park) and Ten [Thousand Islands](https://www.britannica.com/place/Thousand-Islands) National Wildlife Refuge were in the path, and some estimates claim that as much as 10 feet (3 meters) of storm surge may have occurred there. By September 11 Irma had weakened to a tropical storm near [Gainesville](https://www.britannica.com/place/Gainesville-Florida), with its strongest winds moving over northern Florida and southern [Georgia](https://www.britannica.com/place/Georgia-state). The system reached [Alabama](https://www.britannica.com/place/Alabama-state) on September 12 with wind speeds of 25 knots (29 miles \[46 km\] per hour), and it dropped heavy rain on [North Carolina](https://www.britannica.com/place/North-Carolina-state) and [South Carolina](https://www.britannica.com/place/South-Carolina) as well. Remnant winds and rain reached southeast [Missouri](https://www.britannica.com/place/Missouri-state) the next day.
## Damage
[](https://cdn.britannica.com/25/276225-050-F86E80D7/Hurricane-Irma-2017-Caused-Destruction-Flooding-Across-Caribbean-Prompting-Evacuation-Operations.jpg)
[Flooding from Hurricane Irma](https://cdn.britannica.com/25/276225-050-F86E80D7/Hurricane-Irma-2017-Caused-Destruction-Flooding-Across-Caribbean-Prompting-Evacuation-Operations.jpg)Storm surge and powerful waves from the hurricane caused severe flooding along the north coast of Cuba.
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Hurricane Irma caused [immense](https://www.britannica.com/dictionary/immense) property damage, estimated between \$64 billion and \$90 billion. The U.S. alone incurred damage close to \$50 billion, which makes Irma one of the [costliest tropical cyclones](https://www.britannica.com/science/List-of-the-Costliest-Hurricanes-in-the-United-States) in the country’s history. In the United States and the Caribbean, 47 direct deaths were reported, most of which were attributed to drowning or wind-related accidents. An additional 82 indirect deaths were reported in the United States, with 77 of these occurring in Florida. Irma struck many small islands in the Caribbean at peak or near-peak intensity. Barbuda was devastated, with nearly 95 percent of structures affected, leaving the island nearly uninhabitable. Survivors sought shelter on its sister island of [Antigua](https://www.britannica.com/place/Antigua-and-Barbuda), 25 miles (40 km) away. Economic costs for rebuilding were estimated at more than \$222 million.
[](https://cdn.britannica.com/05/274305-050-B35C08CD/hurricanes-by-numbers-named-facts.jpg)
[Hurricane-name retirement](https://cdn.britannica.com/05/274305-050-B35C08CD/hurricanes-by-numbers-named-facts.jpg)Removing the name of a hurricane from a storm list is typically done when a named storm is so costly or so deadly that reusing and retaining it would seem insensitive.
(more)
Satellite imagery from the [British Virgin Islands](https://www.britannica.com/place/British-Virgin-Islands) and the [U.S. Virgin Islands](https://www.britannica.com/place/United-States-Virgin-Islands) taken after Irma revealed [widespread](https://www.britannica.com/dictionary/widespread) deforestation, showing swaths of empty, brown landscape, as Irma’s wind had stripped the land of vegetation. In Cuba, Irma—the first category 5 hurricane to hit the island directly since 1924—damaged more than 150,000 homes. Nearly 15,000 of those were completely destroyed.
The Bahamas had ordered the largest evacuation in the country’s history ahead of Irma’s arrival, and the central and northwestern Bahamas lay well beyond Irma’s most powerful winds. However, many of the islands still saw tropical storm conditions and sustained minor damage. Seventy percent of the houses on Great Inagua Island were reportedly damaged.
In the United States Irma hit less than two weeks after [Hurricane Harvey](https://www.britannica.com/event/Hurricane-Harvey), marking the first time the continental U.S. had seen two category 4 storms in one season since recordkeeping began in 1851. The storm produced 21 tornadoes in Florida and 4 in South Carolina. More than 6 million Florida residents were evacuated, one of the largest evacuations in U.S. history. Most of the structural damage was confined to the [Florida Keys](https://www.britannica.com/place/Florida-Keys), with 25 percent of buildings destroyed. Irma also affected the agricultural industry; losses in this sector were estimated at \$2.5 billion.
## Aftermath
[](https://cdn.britannica.com/52/264452-050-B7C72142/Storm-surge-illustration-Hurricane-Katrina-Ian-Irma.jpg)
[Storm surge](https://cdn.britannica.com/52/264452-050-B7C72142/Storm-surge-illustration-Hurricane-Katrina-Ian-Irma.jpg)A graphic comparing the heights of the water driven inland by Hurricane Ian (2022), Hurricane Irma (2017), and Hurricane Katrina (2005).
(more)
Irma left lasting effects on the [communities](https://www.merriam-webster.com/dictionary/communities) in its path. By 2025 most displaced residents of Barbuda had returned, but in the wake of the destruction, disputes over communal land ownership intensified. Many residents [alleged](https://www.merriam-webster.com/dictionary/alleged) that the government was using the hurricane’s aftermath as an opportunity to pursue billionaire-investor-friendly development, challenging the island’s long-standing system of [collective](https://www.merriam-webster.com/dictionary/collective) land rights.
In the United States the [Federal Emergency Management Agency](https://www.britannica.com/topic/Federal-Emergency-Management-Agency) (FEMA) [deployed](https://www.merriam-webster.com/dictionary/deployed) emergency housing units and funded road and utility repairs, in addition to distributing more than \$48 million in aid to survivors. Recovery in Florida was a complex, long-term effort, with housing shortages and [infrastructure](https://www.merriam-webster.com/dictionary/infrastructure) strain complicating the issue. Physical and [mental health](https://www.britannica.com/science/mental-hygiene) conditions of evacuees and survivors were adversely affected, and the worsening of respiratory problems, anxiety, and depression were reported even 20 months after the hurricane.
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Almost 60 percent of the Florida [Everglades](https://www.britannica.com/place/Everglades) sustained serious damage. The damage to the [mangroves](https://www.britannica.com/plant/mangrove), pinelands, and hardwood hammocks, which are the preferred [habitats](https://www.britannica.com/science/habitat-biology) of the Florida [Key deer](https://www.britannica.com/animal/Key-deer) (*Odocoileus virginianus clavium*), resulted in a 23 percent decline in the animal’s population.
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[natural disaster](https://www.britannica.com/science/natural-disaster)
- [Introduction](https://www.britannica.com/science/natural-disaster)
- [Types](https://www.britannica.com/science/natural-disaster#ref353970)
- [Frequency and disaster patterns](https://www.britannica.com/science/natural-disaster#ref353971)
- [Damage and deaths](https://www.britannica.com/science/natural-disaster#ref353972)
- [Disaster warning systems](https://www.britannica.com/science/natural-disaster#ref353973)
[References & Edit History](https://www.britannica.com/science/natural-disaster/additional-info) [Related Topics](https://www.britannica.com/facts/natural-disaster)
[Images & Videos](https://www.britannica.com/science/natural-disaster/images-videos)
[](https://cdn.britannica.com/41/230741-050-DE5AED6F/Open-plain-with-cracked-mud-and-clear-sky.jpg)
[](https://www.britannica.com/video/natural-disasters-impact/-304763)
[](https://cdn.britannica.com/94/227994-050-7A77244B/hurricane-in-the-gulf-of-Mexico-by-NASA-space.jpg) [](https://cdn.britannica.com/29/93629-050-BE1D6ED7/landslide-part-town-earthquake-San-Salvador-El-2001.jpg) [](https://cdn.britannica.com/57/5457-050-40B0E740/ring-volcanoes-arcs-tectonic-plate-boundaries-Pacific.jpg) [](https://cdn.britannica.com/51/23851-050-EF432F24/Map-frequency-tornadoes-range-Texas-Nebraska-Tornado.jpg) [](https://cdn.britannica.com/28/197428-050-A4257FF9/views-New-Orleans-foreground-Louisiana-Superdome-Hurricane-July-29-2015.jpg) [](https://cdn.britannica.com/87/192187-050-B42C0C0B/Doppler-radars-signal-echo-target-National-Weather.jpg)
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[](https://cdn.britannica.com/41/230741-050-DE5AED6F/Open-plain-with-cracked-mud-and-clear-sky.jpg)
[drought](https://cdn.britannica.com/41/230741-050-DE5AED6F/Open-plain-with-cracked-mud-and-clear-sky.jpg) Droughts occur when evaporation and transpiration (the movement of water in the soil through plants into the air) exceed precipitation for a considerable period.
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# natural disaster
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[Michele Metych Michele Metych is the lead editor for *Today in History* at *Encyclopædia Britannica*.](https://www.britannica.com/editor/Michele-Metych/9760897)
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- What is a natural disaster?
- What are some common types of natural disasters?
- How do natural disasters happen?
- What effects can natural disasters have on people and the environment?
- How do people prepare for and respond to natural disasters?
- How can communities reduce the damage caused by natural disasters?
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**natural disaster**, any calamitous occurrence generated by the effects of natural, rather than human-driven, phenomena that produces great loss of [human](https://www.britannica.com/topic/human-being) [life](https://www.britannica.com/science/life) or destruction of the natural [environment](https://www.britannica.com/science/environment), private property, or public [infrastructure](https://www.merriam-webster.com/dictionary/infrastructure). A natural [disaster](https://www.britannica.com/science/disaster) may be caused by [weather](https://www.britannica.com/science/weather) and [climate](https://www.britannica.com/science/climate-meteorology) events or by [earthquakes](https://www.britannica.com/science/earthquake-geology), [landslides](https://www.britannica.com/science/landslide), and other occurrences that originate at [Earth](https://www.britannica.com/place/Earth)’s surface or within the [planet](https://www.britannica.com/science/planet) itself. No spot on Earth is immune from a natural disaster; however, certain types of disasters are often limited to or occur more frequently in specific geographic regions.
## Types
[1 of 2](https://www.britannica.com/video/natural-disasters-impact/-304763)
Can we predict natural disasters?Protecting against natural disasters requires a multipronged approach.
(more)
[See all videos for this article](https://www.britannica.com/science/natural-disaster/images-videos)
[2 of 2](https://cdn.britannica.com/94/227994-050-7A77244B/hurricane-in-the-gulf-of-Mexico-by-NASA-space.jpg)
[tropical cyclone](https://cdn.britannica.com/94/227994-050-7A77244B/hurricane-in-the-gulf-of-Mexico-by-NASA-space.jpg)In the North Atlantic Ocean and the eastern North Pacific, tropical cyclones are called hurricanes, and, in the western North Pacific, these storms are referred to as typhoons.
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Weather- and climate-driven natural disasters include [flooding](https://www.britannica.com/science/flood) caused by heavy [rains](https://www.britannica.com/science/rain) associated with hurricanes and typhoons ([tropical cyclones](https://www.britannica.com/science/tropical-cyclone)) and other intense storms; [drought](https://www.britannica.com/science/drought), [famine](https://www.britannica.com/science/famine), and [wildfires](https://www.britannica.com/science/wildfire) brought on by [heat waves](https://www.britannica.com/science/heat-wave-meteorology) and shifts in [precipitation](https://www.britannica.com/science/precipitation) patterns; [wind](https://www.britannica.com/science/wind)\-generated devastation caused by tropical cyclones, [tornadoes](https://www.britannica.com/science/tornado), [derechos](https://www.britannica.com/science/derecho), and other [windstorms](https://www.britannica.com/science/windstorm); and damage and loss of life caused by [blizzards](https://www.britannica.com/science/blizzard) and heavy snowfalls. Earth-driven natural disasters include large [volcanic eruptions](https://www.britannica.com/science/volcanism) (which produce [lava](https://www.britannica.com/science/lava-volcanic-ejecta) flows, explosions, [toxic](https://www.britannica.com/dictionary/toxic) gas clouds, ash falls, and [pyroclastic flows](https://www.britannica.com/science/pyroclastic-flow) that damage populated areas) and strong earthquakes (which result from the sudden fracturing of Earth’s [crust](https://www.britannica.com/science/crust-mantle-model)) powerful enough to damage or destroy built-up areas near their origin points.
[](https://cdn.britannica.com/29/93629-050-BE1D6ED7/landslide-part-town-earthquake-San-Salvador-El-2001.jpg)
[landslide](https://cdn.britannica.com/29/93629-050-BE1D6ED7/landslide-part-town-earthquake-San-Salvador-El-2001.jpg)A landslide is a movement downslope of a mass of rock, debris, earth, or soil (soil being a mixture of earth and debris).
(more)
Some phenomena that produce natural disasters may be caused by a combination of several different forces. For example, landslides (the movement of large masses of [rock](https://www.britannica.com/science/rock-geology), debris, and [soil](https://www.britannica.com/science/soil) downslope) may be caused by rains that saturate the soil on an unstable slope, or they may be triggered by earthquakes. In a similar manner, the buildup of [snow](https://www.britannica.com/science/snow-weather) on [mountain](https://www.britannica.com/science/mountain-landform) slopes increases the risks of localized [avalanches](https://www.britannica.com/science/avalanche). [Tsunamis](https://www.britannica.com/science/tsunami), catastrophic ocean [waves](https://www.britannica.com/science/wave-water) that can rise as high as 30 metres (about 100 feet) above normal [sea level](https://www.britannica.com/science/sea-level), are produced by submarine earthquakes, underwater or coastal landslides, volcanic eruptions, or [meteor](https://www.britannica.com/science/meteor) or [comet](https://www.britannica.com/science/comet-astronomy) impacts. The largest tsunamis are fast-moving waves that can travel across oceans to wreak [havoc](https://www.britannica.com/dictionary/havoc) in coastal areas separated thousands of kilometres from one another.
## Frequency and disaster patterns
[1 of 2](https://cdn.britannica.com/57/5457-050-40B0E740/ring-volcanoes-arcs-tectonic-plate-boundaries-Pacific.jpg)
[Pacific Rim](https://cdn.britannica.com/57/5457-050-40B0E740/ring-volcanoes-arcs-tectonic-plate-boundaries-Pacific.jpg)The ring of active volcanoes, volcanic arcs (including the Aleutian Islands at the top), and tectonic plate boundaries that frame the Pacific Ocean.
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[2 of 2](https://cdn.britannica.com/51/23851-050-EF432F24/Map-frequency-tornadoes-range-Texas-Nebraska-Tornado.jpg)
[Tornado Alley](https://cdn.britannica.com/51/23851-050-EF432F24/Map-frequency-tornadoes-range-Texas-Nebraska-Tornado.jpg)Map of the average annual frequency of tornadoes in the United States, showing the range of Tornado Alley from Texas through Nebraska.
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Certain types of natural disasters are more likely to occur in specific geographic regions, and in some places these events occur with seasonal regularity, as in the spring [tornado](https://www.britannica.com/science/tornado) season in the [United States](https://www.britannica.com/place/United-States) or the summer-and-fall [hurricane](https://www.britannica.com/science/hurricane-weather) season in the [Atlantic Ocean](https://www.britannica.com/place/Atlantic-Ocean), [Caribbean Sea](https://www.britannica.com/place/Caribbean-Sea), and the [Gulf of Mexico](https://www.britannica.com/place/Gulf-of-Mexico-Gulf-of-America). Earthquakes and volcanic eruptions are most frequent near [tectonic plate](https://www.britannica.com/science/plate-tectonics) boundaries, and an especially active boundary exists between the Indo-Australian and Eurasian plates.
The [World Meteorological Organization](https://www.britannica.com/topic/World-Meteorological-Organization) (WMO)—a [United Nations](https://www.britannica.com/topic/United-Nations) (UN) agency that monitors Earth’s land, [water](https://www.britannica.com/science/water), and [atmosphere](https://www.britannica.com/science/atmosphere)—reported in 2021 that the number of natural disasters per decade showed a fivefold increase from 1979 to 2019, and [data](https://www.britannica.com/dictionary/data) collected in the EM-DAT, an international disaster database maintained by the Center for Research on the Epidemiology of Disasters, Brussels, indicate that more than 300 disasters have been tallied each year since 1998. Though many natural disasters are neither preventable nor largely predictable, the WMO report notes that [global warming](https://www.britannica.com/science/global-warming)—an increasingly human-driven phenomenon generated by the emission of [greenhouse gases](https://www.britannica.com/science/greenhouse-gas), specifically those released by the [combustion](https://www.britannica.com/science/combustion) of [fossil fuels](https://www.britannica.com/science/fossil-fuel)—is increasing the frequency of weather- and climate-related natural disasters, such as droughts, heat waves, increasingly intense hurricanes, and flooding due to sea-level rise. Warmer temperatures are causing more extreme weather events by delivering more precipitation to some areas—which may be unused to receiving heavy rains and snows, increasing flooding risk—while delivering less to other areas that rely on it, increasing [drought](https://www.britannica.com/dictionary/drought) risk. In addition, reliable sources of rainfall, such as the [South Asian monsoon](https://www.britannica.com/science/monsoon), on which agriculture of the [Indian subcontinent](https://www.britannica.com/place/Indian-subcontinent) has long depended, are becoming less predictable, and rain events have become more violent and dangerous, damaging crops and producing more intense flooding. This change has subjected some areas under the monsoon’s influence to extended drought conditions, whereas other areas receive too much rainfall, a pattern that scientists predict will worsen in the 21st century.
## Damage and deaths
[](https://cdn.britannica.com/28/197428-050-A4257FF9/views-New-Orleans-foreground-Louisiana-Superdome-Hurricane-July-29-2015.jpg)
[Superdome](https://cdn.britannica.com/28/197428-050-A4257FF9/views-New-Orleans-foreground-Louisiana-Superdome-Hurricane-July-29-2015.jpg)Aerial views of downtown New Orleans, Louisiana, with the Superdome in the foreground: (left) on August 30, 2005, a day after Hurricane Katrina struck the city, and (right) again some 10 years later on July 29, 2015.
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The costs of individual natural disasters frequently reach the tens of billions of dollars. Such costs may be associated with damage to crops, buildings, and [infrastructure](https://www.britannica.com/dictionary/infrastructure) that occurs annually in areas prone to tropical cyclone activity or heavy seasonal rains, with some events, such as the [Pakistan](https://www.britannica.com/place/Pakistan) floods of 2022 and [Hurricane Katrina](https://www.britannica.com/event/Hurricane-Katrina) (which struck the southern United States in 2005), costing more than \$30 billion and \$186 billion, respectively. Similarly, costs associated with earthquakes, which occur less regularly, can be high (such as [China](https://www.britannica.com/place/China)’s [Sichuan earthquake of 2008](https://www.britannica.com/event/Sichuan-earthquake-of-2008) and [Japan](https://www.britannica.com/place/Japan)’s [Kōbe earthquake of 1995](https://www.britannica.com/event/Kobe-earthquake-of-1995), which incurred costs estimated at more than \$86 billion and more than \$100 billion, respectively).
The number of [deaths](https://www.britannica.com/science/death) from natural disasters also varies by location and the intensity of the event; however, the overall [trend](https://www.britannica.com/dictionary/trend) points to a decline from several hundreds of thousands of deaths annually during the first half of the 20th century to roughly 45,000 deaths globally each year. The number of deaths also varies widely from year to year, with smaller natural disasters (or natural disasters occurring in areas far from human settlement) killing few and shockingly large disasters producing truly massive losses of life. Some of the most notable catastrophic disasters in history include the [Indian Ocean tsunami of 2004](https://www.britannica.com/event/Indian-Ocean-tsunami-of-2004) (which killed more than 225,000 people), the [Tangshan earthquake of 1976](https://www.britannica.com/event/Tangshan-earthquake-of-1976) (which resulted in more than 242,000 deaths), the [2010 Haiti earthquake](https://www.britannica.com/event/2010-Haiti-earthquake) (which by some estimates may have killed at least 300,000 people), and China’s [Shaanxi province earthquake of 1556](https://www.britannica.com/event/Shaanxi-province-earthquake-of-1556) (which killed more than 800,000 people).
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Although deaths from natural disasters have decreased overall, people in lower-income countries often suffer disproportionately, because these locations have fewer resources and thus greater vulnerability to the elements and to [food insecurity](https://www.britannica.com/topic/food-insecurity). In contrast, highly developed countries have better infrastructure (for communications, evacuation procedures, the movement of resources, and the delivery of medical services). In addition, high-income countries can [implement](https://www.merriam-webster.com/dictionary/implement) policies that limit construction in flood-prone areas or [mandate](https://www.merriam-webster.com/dictionary/mandate) the construction of more earthquake-resistant homes, office buildings, and other structures, thereby reducing the risk of [crushing injury](https://www.britannica.com/science/crush-injury) and death stemming from building collapses. Consequently, relatively few people die from earthquakes in [California](https://www.britannica.com/place/California-state), a location well-known for its strong building codes with respect to withstanding earthquakes, compared with places such as [Iran](https://www.britannica.com/place/Iran) and Pakistan, where building codes are either less stringent or whose codes frequently go unenforced.
## Disaster warning systems
[](https://cdn.britannica.com/87/192187-050-B42C0C0B/Doppler-radars-signal-echo-target-National-Weather.jpg)
[Doppler radar](https://cdn.britannica.com/87/192187-050-B42C0C0B/Doppler-radars-signal-echo-target-National-Weather.jpg)Doppler radars, such as this one operated by the U.S. National Weather Service at New Underwood, South Dakota, extract the Doppler frequency shift of the echo produced by a moving target by noting how much the frequency of the received signal differs from the frequency of the signal that was transmitted.
(more)
Advances in [weather forecasting](https://www.britannica.com/science/weather-forecasting) and advances in land-based seismic sensors and sensors placed aboard [satellites](https://www.britannica.com/science/satellite), aircraft, and stationary [buoys](https://www.britannica.com/technology/buoy) floating in the world’s [oceans](https://www.britannica.com/science/ocean) have led to the development of various kinds of early warning systems. In some cases, these systems are capable of predicting or accurately classifying the strength of the physical forces that generate natural disasters before they cause damage. The perhaps most [widespread](https://www.britannica.com/dictionary/widespread) and best known of these systems are those used by national [weather bureaus](https://www.britannica.com/science/weather-bureau) that classify, track, and predict various weather events and issue bulletins about storms and other weather and climate phenomena affecting their land areas and sea zones. National weather bureaus are often made up of a network of numerous local offices spread across a country that gauge local weather conditions several times per day. Data collected by these offices can be used to develop weather models that help to predict the strength of a [storm](https://www.britannica.com/science/storm), as well as its location, days in advance of its arrival in a local area.
Related Topics:
[12 of the World’s Deadliest Natural Disasters](https://www.britannica.com/list/6-of-the-worlds-deadliest-natural-disasters)
[10 Deadliest Typhoons in History](https://www.britannica.com/science/10-Deadliest-Typhoons-in-History)
[8 Nonhuman Casualties of Hurricanes](https://www.britannica.com/list/8-nonhuman-casualties-of-hurricanes)
[10 of the World’s Largest Fires](https://www.britannica.com/science/10-of-the-worlds-largest-fires)
[When Katrina Struck](https://www.britannica.com/story/when-katrina-struck)
*(Show more)*
On the Web:
[National Center for Biotechnology Information - PubMed Central - Natural Disasters](https://pmc.ncbi.nlm.nih.gov/articles/PMC7171902/) (Mar. 20, 2026)
*(Show more)*
[See all related content](https://www.britannica.com/facts/natural-disaster)
In addition, specialized units within national governments—such as the China Earthquake Administration, the Japan Meteorological Agency, the United Kingdom’s Met Office, India’s National Center of Seismology, the U.S. [National Oceanic and Atmospheric Administration](https://www.britannica.com/topic/National-Oceanic-and-Atmospheric-Administration), and the U.S. Geological Survey—monitor specific physical forces capable of causing the most damaging and deadly natural disasters (that is, earthquakes, tsunamis, [droughts](https://www.britannica.com/dictionary/droughts), flooding, and winds driven by tornadoes and tropical cyclones). Many of these organizations within specific countries cooperate with their counterparts in others or assist international organizations, such as the WMO and the International Tsunami Information Center, to issue warnings, develop international safety standards, and assess the risks associated with forces that affect several countries or the planet as a whole. Some early warning systems even look beyond Earth’s atmosphere; the near-Earth objects system operated by the [European Space Agency](https://www.britannica.com/topic/European-Space-Agency) and the Scout and Sentry impact hazard systems run by [NASA](https://www.britannica.com/topic/NASA) in the United States are a few of several systems designed to detect, track, and predict the risk associated with [asteroids](https://www.britannica.com/science/asteroid), comets, and other extraterrestrial objects capable of striking Earth.
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External Websites
- [Salt Lake Community College Pressbooks - Physical Geography and Natural Disasters - Understanding Natural Disasters](https://slcc.pressbooks.pub/physicalgeography/chapter/1-5/)
- [International Federation of Red Cross and Red Crescent Societies - What is a disaster?](https://www.ifrc.org/our-work/disasters-climate-and-crises/what-disaster)
- [Healthdirect - Natural disasters](https://www.healthdirect.gov.au/natural-disasters)
- [U.S. Department of Homeland Security - Natural Disasters](https://www.dhs.gov/natural-disasters)
- [National Center for Biotechnology Information - PubMed Central - Natural Disasters](https://pmc.ncbi.nlm.nih.gov/articles/PMC7171902/) |
| Readable Markdown | Top Questions
- What is a natural disaster?
- What are some common types of natural disasters?
- How do natural disasters happen?
- What effects can natural disasters have on people and the environment?
- How do people prepare for and respond to natural disasters?
- How can communities reduce the damage caused by natural disasters?
**natural disaster**, any calamitous occurrence generated by the effects of natural, rather than human-driven, phenomena that produces great loss of [human](https://www.britannica.com/topic/human-being) [life](https://www.britannica.com/science/life) or destruction of the natural [environment](https://www.britannica.com/science/environment), private property, or public [infrastructure](https://www.merriam-webster.com/dictionary/infrastructure). A natural [disaster](https://www.britannica.com/science/disaster) may be caused by [weather](https://www.britannica.com/science/weather) and [climate](https://www.britannica.com/science/climate-meteorology) events or by [earthquakes](https://www.britannica.com/science/earthquake-geology), [landslides](https://www.britannica.com/science/landslide), and other occurrences that originate at [Earth](https://www.britannica.com/place/Earth)’s surface or within the [planet](https://www.britannica.com/science/planet) itself. No spot on Earth is immune from a natural disaster; however, certain types of disasters are often limited to or occur more frequently in specific geographic regions.
## Types
Weather- and climate-driven natural disasters include [flooding](https://www.britannica.com/science/flood) caused by heavy [rains](https://www.britannica.com/science/rain) associated with hurricanes and typhoons ([tropical cyclones](https://www.britannica.com/science/tropical-cyclone)) and other intense storms; [drought](https://www.britannica.com/science/drought), [famine](https://www.britannica.com/science/famine), and [wildfires](https://www.britannica.com/science/wildfire) brought on by [heat waves](https://www.britannica.com/science/heat-wave-meteorology) and shifts in [precipitation](https://www.britannica.com/science/precipitation) patterns; [wind](https://www.britannica.com/science/wind)\-generated devastation caused by tropical cyclones, [tornadoes](https://www.britannica.com/science/tornado), [derechos](https://www.britannica.com/science/derecho), and other [windstorms](https://www.britannica.com/science/windstorm); and damage and loss of life caused by [blizzards](https://www.britannica.com/science/blizzard) and heavy snowfalls. Earth-driven natural disasters include large [volcanic eruptions](https://www.britannica.com/science/volcanism) (which produce [lava](https://www.britannica.com/science/lava-volcanic-ejecta) flows, explosions, [toxic](https://www.britannica.com/dictionary/toxic) gas clouds, ash falls, and [pyroclastic flows](https://www.britannica.com/science/pyroclastic-flow) that damage populated areas) and strong earthquakes (which result from the sudden fracturing of Earth’s [crust](https://www.britannica.com/science/crust-mantle-model)) powerful enough to damage or destroy built-up areas near their origin points.
[landslide](https://cdn.britannica.com/29/93629-050-BE1D6ED7/landslide-part-town-earthquake-San-Salvador-El-2001.jpg)A landslide is a movement downslope of a mass of rock, debris, earth, or soil (soil being a mixture of earth and debris).
Some phenomena that produce natural disasters may be caused by a combination of several different forces. For example, landslides (the movement of large masses of [rock](https://www.britannica.com/science/rock-geology), debris, and [soil](https://www.britannica.com/science/soil) downslope) may be caused by rains that saturate the soil on an unstable slope, or they may be triggered by earthquakes. In a similar manner, the buildup of [snow](https://www.britannica.com/science/snow-weather) on [mountain](https://www.britannica.com/science/mountain-landform) slopes increases the risks of localized [avalanches](https://www.britannica.com/science/avalanche). [Tsunamis](https://www.britannica.com/science/tsunami), catastrophic ocean [waves](https://www.britannica.com/science/wave-water) that can rise as high as 30 metres (about 100 feet) above normal [sea level](https://www.britannica.com/science/sea-level), are produced by submarine earthquakes, underwater or coastal landslides, volcanic eruptions, or [meteor](https://www.britannica.com/science/meteor) or [comet](https://www.britannica.com/science/comet-astronomy) impacts. The largest tsunamis are fast-moving waves that can travel across oceans to wreak [havoc](https://www.britannica.com/dictionary/havoc) in coastal areas separated thousands of kilometres from one another.
## Frequency and disaster patterns
Certain types of natural disasters are more likely to occur in specific geographic regions, and in some places these events occur with seasonal regularity, as in the spring [tornado](https://www.britannica.com/science/tornado) season in the [United States](https://www.britannica.com/place/United-States) or the summer-and-fall [hurricane](https://www.britannica.com/science/hurricane-weather) season in the [Atlantic Ocean](https://www.britannica.com/place/Atlantic-Ocean), [Caribbean Sea](https://www.britannica.com/place/Caribbean-Sea), and the [Gulf of Mexico](https://www.britannica.com/place/Gulf-of-Mexico-Gulf-of-America). Earthquakes and volcanic eruptions are most frequent near [tectonic plate](https://www.britannica.com/science/plate-tectonics) boundaries, and an especially active boundary exists between the Indo-Australian and Eurasian plates.
The [World Meteorological Organization](https://www.britannica.com/topic/World-Meteorological-Organization) (WMO)—a [United Nations](https://www.britannica.com/topic/United-Nations) (UN) agency that monitors Earth’s land, [water](https://www.britannica.com/science/water), and [atmosphere](https://www.britannica.com/science/atmosphere)—reported in 2021 that the number of natural disasters per decade showed a fivefold increase from 1979 to 2019, and [data](https://www.britannica.com/dictionary/data) collected in the EM-DAT, an international disaster database maintained by the Center for Research on the Epidemiology of Disasters, Brussels, indicate that more than 300 disasters have been tallied each year since 1998. Though many natural disasters are neither preventable nor largely predictable, the WMO report notes that [global warming](https://www.britannica.com/science/global-warming)—an increasingly human-driven phenomenon generated by the emission of [greenhouse gases](https://www.britannica.com/science/greenhouse-gas), specifically those released by the [combustion](https://www.britannica.com/science/combustion) of [fossil fuels](https://www.britannica.com/science/fossil-fuel)—is increasing the frequency of weather- and climate-related natural disasters, such as droughts, heat waves, increasingly intense hurricanes, and flooding due to sea-level rise. Warmer temperatures are causing more extreme weather events by delivering more precipitation to some areas—which may be unused to receiving heavy rains and snows, increasing flooding risk—while delivering less to other areas that rely on it, increasing [drought](https://www.britannica.com/dictionary/drought) risk. In addition, reliable sources of rainfall, such as the [South Asian monsoon](https://www.britannica.com/science/monsoon), on which agriculture of the [Indian subcontinent](https://www.britannica.com/place/Indian-subcontinent) has long depended, are becoming less predictable, and rain events have become more violent and dangerous, damaging crops and producing more intense flooding. This change has subjected some areas under the monsoon’s influence to extended drought conditions, whereas other areas receive too much rainfall, a pattern that scientists predict will worsen in the 21st century.
## Damage and deaths
[Superdome](https://cdn.britannica.com/28/197428-050-A4257FF9/views-New-Orleans-foreground-Louisiana-Superdome-Hurricane-July-29-2015.jpg)Aerial views of downtown New Orleans, Louisiana, with the Superdome in the foreground: (left) on August 30, 2005, a day after Hurricane Katrina struck the city, and (right) again some 10 years later on July 29, 2015.
The costs of individual natural disasters frequently reach the tens of billions of dollars. Such costs may be associated with damage to crops, buildings, and [infrastructure](https://www.britannica.com/dictionary/infrastructure) that occurs annually in areas prone to tropical cyclone activity or heavy seasonal rains, with some events, such as the [Pakistan](https://www.britannica.com/place/Pakistan) floods of 2022 and [Hurricane Katrina](https://www.britannica.com/event/Hurricane-Katrina) (which struck the southern United States in 2005), costing more than \$30 billion and \$186 billion, respectively. Similarly, costs associated with earthquakes, which occur less regularly, can be high (such as [China](https://www.britannica.com/place/China)’s [Sichuan earthquake of 2008](https://www.britannica.com/event/Sichuan-earthquake-of-2008) and [Japan](https://www.britannica.com/place/Japan)’s [Kōbe earthquake of 1995](https://www.britannica.com/event/Kobe-earthquake-of-1995), which incurred costs estimated at more than \$86 billion and more than \$100 billion, respectively).
The number of [deaths](https://www.britannica.com/science/death) from natural disasters also varies by location and the intensity of the event; however, the overall [trend](https://www.britannica.com/dictionary/trend) points to a decline from several hundreds of thousands of deaths annually during the first half of the 20th century to roughly 45,000 deaths globally each year. The number of deaths also varies widely from year to year, with smaller natural disasters (or natural disasters occurring in areas far from human settlement) killing few and shockingly large disasters producing truly massive losses of life. Some of the most notable catastrophic disasters in history include the [Indian Ocean tsunami of 2004](https://www.britannica.com/event/Indian-Ocean-tsunami-of-2004) (which killed more than 225,000 people), the [Tangshan earthquake of 1976](https://www.britannica.com/event/Tangshan-earthquake-of-1976) (which resulted in more than 242,000 deaths), the [2010 Haiti earthquake](https://www.britannica.com/event/2010-Haiti-earthquake) (which by some estimates may have killed at least 300,000 people), and China’s [Shaanxi province earthquake of 1556](https://www.britannica.com/event/Shaanxi-province-earthquake-of-1556) (which killed more than 800,000 people).
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Although deaths from natural disasters have decreased overall, people in lower-income countries often suffer disproportionately, because these locations have fewer resources and thus greater vulnerability to the elements and to [food insecurity](https://www.britannica.com/topic/food-insecurity). In contrast, highly developed countries have better infrastructure (for communications, evacuation procedures, the movement of resources, and the delivery of medical services). In addition, high-income countries can [implement](https://www.merriam-webster.com/dictionary/implement) policies that limit construction in flood-prone areas or [mandate](https://www.merriam-webster.com/dictionary/mandate) the construction of more earthquake-resistant homes, office buildings, and other structures, thereby reducing the risk of [crushing injury](https://www.britannica.com/science/crush-injury) and death stemming from building collapses. Consequently, relatively few people die from earthquakes in [California](https://www.britannica.com/place/California-state), a location well-known for its strong building codes with respect to withstanding earthquakes, compared with places such as [Iran](https://www.britannica.com/place/Iran) and Pakistan, where building codes are either less stringent or whose codes frequently go unenforced.
## Disaster warning systems
[Doppler radar](https://cdn.britannica.com/87/192187-050-B42C0C0B/Doppler-radars-signal-echo-target-National-Weather.jpg)Doppler radars, such as this one operated by the U.S. National Weather Service at New Underwood, South Dakota, extract the Doppler frequency shift of the echo produced by a moving target by noting how much the frequency of the received signal differs from the frequency of the signal that was transmitted.
Advances in [weather forecasting](https://www.britannica.com/science/weather-forecasting) and advances in land-based seismic sensors and sensors placed aboard [satellites](https://www.britannica.com/science/satellite), aircraft, and stationary [buoys](https://www.britannica.com/technology/buoy) floating in the world’s [oceans](https://www.britannica.com/science/ocean) have led to the development of various kinds of early warning systems. In some cases, these systems are capable of predicting or accurately classifying the strength of the physical forces that generate natural disasters before they cause damage. The perhaps most [widespread](https://www.britannica.com/dictionary/widespread) and best known of these systems are those used by national [weather bureaus](https://www.britannica.com/science/weather-bureau) that classify, track, and predict various weather events and issue bulletins about storms and other weather and climate phenomena affecting their land areas and sea zones. National weather bureaus are often made up of a network of numerous local offices spread across a country that gauge local weather conditions several times per day. Data collected by these offices can be used to develop weather models that help to predict the strength of a [storm](https://www.britannica.com/science/storm), as well as its location, days in advance of its arrival in a local area.
In addition, specialized units within national governments—such as the China Earthquake Administration, the Japan Meteorological Agency, the United Kingdom’s Met Office, India’s National Center of Seismology, the U.S. [National Oceanic and Atmospheric Administration](https://www.britannica.com/topic/National-Oceanic-and-Atmospheric-Administration), and the U.S. Geological Survey—monitor specific physical forces capable of causing the most damaging and deadly natural disasters (that is, earthquakes, tsunamis, [droughts](https://www.britannica.com/dictionary/droughts), flooding, and winds driven by tornadoes and tropical cyclones). Many of these organizations within specific countries cooperate with their counterparts in others or assist international organizations, such as the WMO and the International Tsunami Information Center, to issue warnings, develop international safety standards, and assess the risks associated with forces that affect several countries or the planet as a whole. Some early warning systems even look beyond Earth’s atmosphere; the near-Earth objects system operated by the [European Space Agency](https://www.britannica.com/topic/European-Space-Agency) and the Scout and Sentry impact hazard systems run by [NASA](https://www.britannica.com/topic/NASA) in the United States are a few of several systems designed to detect, track, and predict the risk associated with [asteroids](https://www.britannica.com/science/asteroid), comets, and other extraterrestrial objects capable of striking Earth. |
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