Background

Tornadoes can occur anywhere and at any time during the year. In an average year, 800 tornadoes are reported throughout the nation. The most violent tornadoes may have wind speeds of 250 mph or more, and may last for more than an hour. Sometimes multiple tornadoes may occur at the same time. Tornadoes can appear rapidly, so it is important to be familiar with the signs in order to stay prepared.

Early warnings about a likely tornado can help save lives. Weather radar systems are used to detect air movement which could indicate that a tornado may be likely to form. Environmental clues may also suggest that a tornado is forming. Here are some signs to look for:

• Dark, often greenish clouds or sky
• Wall cloud
• Large hail
• Funnel cloud
• Roaring noise

For more information about tornadoes, see Tornadoes... Nature's Most Violent Storms from the National Oceanic and Atmospheric Administration (NOAA).