Tornadoes are one of nature's most violent storms. In an average year, about 1,000 tornadoes are reported across the United States, resulting in 80 deaths and over 1,500 injuries. A tornado is a violently rotating column of air extending from a thunderstorm to the ground. The most violent tornadoes are capable of tremendous destruction with wind speeds of 250 mph or more. Damage paths can be in excess of one mile wide and 50 miles long.

Tornadoes come in all shapes and sizes and can occur anywhere in the U.S. at any time of the year. In the southern states, peak tornado season is March through May, while peak time in the northern states is during the summer. Tornadoes are most likely to occur between 3 and 9 p.m., but can happen all hours of the day or night.

Preparing For Tornadoes

Key Safety Rules

• In a home or building, move to a pre-designated shelter, such as a basement.
If an underground shelter is not available, move to a small interior room or hallway on the lowest floor and get under a sturdy piece of furniture. Put as many walls as possible between you and the outside.
Stay away from windows.
If caught outside in a vehicle, do not try to outrun a tornado. Get out of the vehicle and seek safe shelter. Lie flat in a nearby ditch or depression and cover your head with your hands.
Be aware of flying debris. Flying debris from tornadoes causes most deaths and injuries.
Mobile homes, even if tied down, offer little protection from tornadoes. You should leave a mobile home and go to the lowest floor of a sturdy nearby building or a storm shelter.
Occasionally, tornadoes develop so rapidly that advance warning is not possible. Remain alert for signs of an approaching tornado such as a dark, often greenish sky, large hail, or a loud roar similar to a freight train.

Read more about family disaster preparedness from the National Weather Service, the Federal Emergency Management Agency, and the American Red Cross.

Watches Versus Warnings

Watch: Tornadoes are possible in your area. Remain alert for approaching storms and rapidly changing weather conditions. Know what counties or parishes are in the watch area by listening to NOAA Weather Radio or your local television outlets.

Warning: A tornado has been sighted or indicated by weather radar. A warning indicates imminent danger to life and property to those in the path of the storm, move to your pre-designated place of safety.

Fujita Tornado Damage Scale

Category F0: Light Damage (less than 73 mph); Some damage to chimneys; branches broken off trees; shallow-rooted trees pushed over; sign boards damaged.

Category F1: Moderate Damage (73 to 112 mph); Peels surface off roofs; mobile homes pushed off foundations or overturned; moving autos blown off road.

Category F2: Considerable Damage (113 to157 mph); Roofs torn off frame houses; mobile homes demolished; boxcars overturned; large trees snapped or uprooted; light-object missiles generated; cars lifted off ground.

Category F3: Severe Damage (158 to 206 mph); Roofs and some walls torn off well-constructed houses; trains overturned; most trees uprooted; heavy cars lifted off ground and thrown.

Category F4: Devastating Damage (207 to 260 mph); Well-constructed houses leveled; structures with weak foundations blown off some distance; cars thrown and large missiles generated.

Category F5: Incredible Damage (261 to 318 mph); Strong-frame houses lifted off foundations and swept away; automobile sized missiles fly through the air in excess of 100 meters (109 yards); trees debarked; incredible phenomena will occur.

IMPORTANT NOTE ABOUT F-SCALE WINDS: Do not use F-scale winds literally. These wind speed numbers are estimates and have never been scientifically verified. Different wind speeds may cause similar-looking damage from place to place — even from building to building. Without a thorough engineering analysis of tornado damage in any event, the actual wind speeds needed to cause that damage are unknown.

Courtesy of the National Oceanic and Atmospheric Administration — U.S. Dept. of Commerce. Visit their website for more information.