Fact Sheet: Severe Thunderstroms, 2011

Severe thunderstorms frequently visit Iowa year. Each year on average Iowa sees about 48 tornadoes, tens of flash flood events, hundreds of severe thunderstorms and thousands of non-severe thunderstorms. By definition, a severe thunderstorm must contain hail that is one inch in diameter or larger, straight line winds of 58 mph or stronger and/or a tornado. The National Weather Service issues severe thunderstorm and tornado watches and warnings for severe thunderstorms.