Some of the 18 natural hazards included in the National Risk Index of FEMA
Hot and dry conditions Heat waves A heat wave is a period of unusually and excessively hot weather. Heat waves used to be rare, requiring specific combinations of
weather events to take place, such as
temperature inversions,
katabatic winds, or other phenomena. Since the turn of this century, under the continuing pressure of global warming, many areas have experienced peaks of temperatures, along with more frequent, more intense, more prolonged warming events than ever met on record. This is notably the case in many ocean regions such as the Mediterranean Sea. On land heat waves coupled with severe winds are now causing hundreds of major wildfires every year, burning thousands of square kilometers of forests, and threatening the very heart of cities as observed in the January 2025 megafires that destroyed several sectors of Los Angeles.
Droughts Well-known historical
droughts include the 1997–2009
Millennium Drought in Australia which led to a water supply crisis across much of the country. As a result, many desalination plants were built for the first time (
see list). In 2011, the State of
Texas lived under a drought emergency declaration for the entire calendar year and suffered severe economic losses. The drought caused the
Bastrop fires.
Duststorms Firestorms Wildfires in
California.
Wildfires are large fires which often start in
wildland areas. Common causes include
lightning and
drought but wildfires may also be started by human negligence or
arson. They can spread to populated areas and thus be a threat to humans and property, as well as
wildlife. One example for a notable
wildfire is the 1871
Peshtigo Fire in the United States, which killed at least 1700 people. Another one is the 2009 Victorian bushfires in Australia (collectively known as "
Black Saturday bushfires"). In that year, a summer heat wave in Victoria, Australia, created conditions which fueled the massive
bushfires in 2009.
Melbourne experienced three days in a row of temperatures exceeding 40 °C (104 °F), with some regional areas sweltering through much higher temperatures.
Storms and heavy rain Floods during the
2000 Mozambique flood A
flood is an overflow of water that 'submerges' land. The EU
Floods Directive defines a flood as a temporary covering of land that is usually dry with water. In the sense of 'flowing water', the word may also be applied to the inflow of the
tides. Flooding may result from the volume of a body of water, such as a
river or
lake, becoming higher than usual, causing some of the water to escape its usual boundaries. While the size of a lake or other body of water will vary with seasonal changes in precipitation and snow melt, a flood is not considered significant unless the water covers land used by humans, such as a village, city or other inhabited area, roads or expanses of farmland.
Thunderstorms Severe storms, dust clouds and volcanic eruptions can generate
lightning. Apart from the damage typically associated with storms, such as winds, hail and flooding, the lightning itself can damage buildings, ignite fires and kill by direct contact. Most deaths from lightning occur in the poorer countries of the Americas and Asia, where lightning is common and
adobe mud brick housing provides little protection.
Tropical cyclone making landfall in
Jamaica as a Category 5 hurricane in October
2025.
Typhoon,
cyclone,
cyclonic storm and
hurricane are different names for the same phenomenon: a
tropical storm that forms over an ocean. It is caused by evaporated
water that comes off of the
ocean and becomes a
storm. It is characterized by strong winds, heavy rainfall and thunderstorms. The determining factor on which term is used is based on where the storm originates. In the Atlantic and Northeast Pacific, the term "hurricane" is used; in the Northwest Pacific, it is referred to as a "typhoon"; a "cyclone" occurs in the South Pacific and Indian Ocean. The deadliest hurricane ever was the
1970 Bhola cyclone; the deadliest Atlantic hurricane was the
Great Hurricane of 1780, which devastated Martinique, St. Eustatius and Barbados. Another notable hurricane is
Hurricane Katrina, which devastated the Gulf Coast of the United States in 2005. Hurricanes may
become more intense and produce more heavy rainfall as a consequence of human-induced
climate change.
Tornadoes photographed during the
2011 Super Outbreak, the most intense tornado outbreak on record. A
tornado is a violent and dangerous rotating column of air that is in contact with both the surface of the Earth and a
cumulonimbus cloud, or, in rare cases, the base of a
cumulus cloud. It is also referred to as a
twister or a
cyclone, although the word
cyclone is used in meteorology in a wider sense to refer to any closed
low pressure circulation. Tornadoes come in many shapes and sizes but typically take the form of a visible
condensation funnel, the narrow end of which touches the Earth and is often encircled by a cloud of
debris and
dust. Tornadoes can occur one at a time, or can occur in large
tornado outbreaks associated with
supercells or in other large areas of thunderstorm development. Most tornadoes have wind speeds of less than , are approximately across, and travel a few kilometers before dissipating. The
most extreme tornadoes can attain wind speeds of more than , attain a width exceeding across, and stay on the ground for perhaps more than .
Cold-weather events Blizzards in
Maryland in 2009 Blizzards are severe
winter storms characterized by heavy snow and strong winds. When high winds stir up snow that has already fallen, it is known as a
ground blizzard. Blizzards can impact local economic activities, especially in regions where snowfall is rare. The
Great Blizzard of 1888 affected the United States, when many tons of wheat crops were destroyed. In Asia, the
1972 Iran blizzard and the
2008 Afghanistan blizzard, were the deadliest blizzards in history; in the former, an area the size of Wisconsin was entirely buried in snow. The
1993 Superstorm originated in the Gulf of Mexico and traveled north, causing damage in 26 American states as well as in Canada and leading to more than 300 deaths.
Hailstorms stone, about in diameter Hail is precipitation in the form of ice that does not melt before it hits the ground. Hailstorms are produced by thunderstorms. Hailstones usually measure between in diameter. These can damage the location in which they fall. Hailstorms can be especially devastating to
farm fields, ruining crops and damaging equipment. A particularly damaging hailstorm hit
Munich, Germany, on July 12, 1984, causing about $2 billion in
insurance claims. == Multi-hazard analysis ==