Tornadoes are nature’s most violent storms. Spawned from powerful thunderstorms, tornadoes can cause fatalities and devastate a neighborhood in seconds. A tornado appears as a rotating, funnel-shaped cloud that extends from a thunderstorm to the ground with whirling winds that can reach 300 miles per hour. Damage paths can be in excess of one mile wide and 50 miles long. Every state is at some risk from this hazard.
Some tornadoes are clearly visible, while rain or nearby low-hanging clouds obscure others. Occasionally, tornadoes develop so rapidly that little, if any, advance warning is possible.

Before a tornado hits, the wind may die down and the air may become very still. A cloud of debris can mark the location of a tornado even if a funnel is not visible. Tornadoes generally occur near the trailing edge of a thunderstorm. It is not uncommon to see clear, sunlit skies behind a tornado.

The following are facts about tornadoes:

• They may strike quickly, with little or no warning.
• They may appear nearly transparent until dust and debris are picked up or a cloud forms in the funnel.
• The average tornado moves Southwest to Northeast, but tornadoes have been known to move in any direction.
• The average forward speed of a tornado is 30 MPH, but may vary from stationary to 70 MPH.
• Tornadoes can accompany tropical storms and hurricanes as they move onto land.
  Waterspouts are tornadoes that form over water.
• Tornadoes are most frequently reported east of the Rocky Mountains during spring and summer months.
• Peak tornado season in the southern states is March through May; in the northern states, it is late spring through early summer.
• Tornadoes are most likely to occur between 3 p.m. and 9 p.m., but can occur at any time.

All thunderstorms are dangerous. Every thunderstorm produces lightning. In the United States, an average of 300 people are injured and 80 people are killed each year by lightning. Although most lightning victims survive, people struck by lightning often report a variety of long-term, debilitating symptoms. Other associated dangers of thunderstorms include tornadoes, strong winds, hail, and flash flooding. Flash flooding is responsible for more fatalities more than 140 annually than any other thunderstorm associated hazard.

Dry thunderstorms that do not produce rain that reaches the ground are most prevalent in the western United States. Falling raindrops evaporate, but lightning can still reach the ground and can start wildfires.

• They may occur singly, in clusters, or in lines.
• Some of the most severe occur when a single thunderstorm affects one location for an extended time.
• Thunderstorms typically produce heavy rain for a brief period, anywhere from 30 minutes to an hour.
• Warm, humid conditions are highly favorable for thunderstorm development.
• About 10 percent of thunderstorms are classified as severe—one that produces hail at least three-quarters of an inch in diameter, has winds of 58 miles per hour or higher, or produces a tornado.