Hurricanes and tornadoes both spin, but each has its own fuel. A hurricane runs on warm ocean water. Water evaporates into vapor and rises. The warmed air is pulled into the column of clouds. The warmer the water, the more powerful the storm is likely to grow. A tropical cyclone is a rotating low-pressure weather system. It has organized thunderstorms but no fronts. Its eye is a relatively calm area, typically 20 to 40 miles across. The average hurricane spreads across about 340 miles (547 km), far wider than any tornado. Hurricanes usually weaken when they move over land.

A tornado starts with a thunderstorm. Moisture and rising unstable air are two basic ingredients of a thunderstorm. A supercell is a long-lived, organized thunderstorm. It has a tilted, rotating updraft, a rising current of air. That updraft can be up to 10 miles wide and 50,000 feet tall. It can be there 20 to 60 minutes before a tornado forms. A wall cloud that may produce a tornado can exist for 10 to 20 minutes before the tornado appears, but not always.

Tornadoes come in many sizes. Some are quite narrow, only about 250 feet (75 meters) across where they touch the ground. Others are much bigger and can be up to two miles across. A tornado can move from almost standing still to faster than 60 miles per hour. It may be on the ground for an instant or for several hours. The average is about five minutes. Tornadoes have been reported in all fifty states. As of November 2026, about 1,200 tornadoes touch down in the United States each year.

Forecasters can see a tornado before it reaches the ground. A pattern in NSSL Doppler radar data is called the Tornado Vortex Signature. It shows high above the ground first. Trained storm spotters tell the National Weather Service what they see. As of November 2026, the SKYWARN program has between 350,000 and 400,000 trained volunteer severe weather spotters. A tornado watch means tornadoes are possible in and near an area. A tornado warning means a tornado has been seen or shown by radar.

The Saffir-Simpson Hurricane Wind Scale is a 1 to 5 rating. It is based only on a hurricane's maximum sustained wind speed. Category 3, the first major category, means sustained winds of 111 to 129 mph. Category 5, the top of the scale, is sustained winds of 157 mph or higher. Tornadoes have a different scale. Enhanced Fujita ratings EF0 and EF1 are called weak, EF2 and EF3 strong, and EF4 and EF5 violent. An EF0 tornado, the weakest category, has gusts up to 85 mph (135 kph).

A tropical storm has winds of at least 39 mph, and storms that strong get a name. Different regions use their own names once a tropical cyclone has winds of at least 65 knots (74 mph). The word hurricane is used in the North Atlantic, the central North Pacific and the eastern North Pacific. In the Pacific north of the Equator and west of the International Dateline, the storms are called typhoons. Atlantic storms have been named from lists started by the National Hurricane Center since 1953. The United States began using women's names for storms that year. Naming has proven to be the fastest way to communicate warnings. It helps avoid confusion among forecasters, media, emergency agencies and the public.

The history of hurricane hunting starts in 1943. Colonel Joe Duckworth of the Army Air Forces flew a single-engine trainer plane through a hurricane for the first time. He showed it could be done. As of November 2026, the Air Force flies a modified Lockheed C-130 called the WC-130J Super Hercules as its hurricane-hunting plane. A Hurricane Hunter mission in a P-3 plane typically lasts 8 to 10 hours. As of November 2026, the NOAA Gulfstream IV jet has flown missions around nearly every Atlantic-based hurricane that threatened the United States since 1997.

A hurricane watch means hurricane conditions are possible in an area. Hurricane conditions are sustained winds of 74 mph or greater. The National Hurricane Center issues the watch 48 hours before it expects tropical storm-force winds. A hurricane warning means those conditions are expected. It is issued 36 hours before tropical storm-force winds. Safety advice for a hurricane includes putting as many walls as you can between you and the outside. Stay away from windows, skylights and glass doors. In a tornado warning, a family goes to a basement or an inside room with no windows.

Words to know

• evaporates: turns to vapor
• supercell: rotating thunderstorm
• updraft: rising air
• typhoons: Pacific hurricanes
• radar: storm-seeing tool
• tropical: near the Equator