Thunderstorm & Hail Basics...
Thunderstorms can produce 4 basic kinds of severe weather...
Tornadoes, strong straight-line winds, flash flood producing rains, and large damaging hail
the National Weather Service (NWS) issues "Severe Thunderstorm Warnings" for
- hail stones 1 inch in diameter or larger (criteria was raised from 3/4" to 1" on April 1, 2009), and/or
- straight-line wind gusts of 58 mph or higher (measured or implied by tree/structural damage)
- Roughly 36% of all severe weather "events" in Wisconsin are hail events in which hailstones are at least 3/4 inch in diameter. Damaging, straight-line wind events make up about 57% of all severe weather events, while tornadoes add up to about 7%
- Serious hailstorms (with hail stones 1.5 inch or larger in diameter) are not common in Wisconsin... however, when they do strike the result is significant property damage. Rarely is a person injured or killed by large hail in Wisconsin.
- The largest hailstone was 5.7" in diameter - near Wausau in May 1921. A 5.5" hail stone fell in Port Edwards on June 7, 2007. A 5" hailstone fell near Waukesha in 2008.
- The peak hail season is April through August, although hail has been reported with thunderstorms in every month of the year.
- The southern half of Wisconsin tends to have the greatest number of hail events...with Dane and La Cross counties leading the way. However, any Wisconsin county can have a serious hailstorm!
- Any given location in Wisconsin will usually experience about 3 days with hail per year.
- On April 13, 2006, one supercell thunderstorm accounted for nearly all of the $420 million in damage that resulted from 3 storms that affected southern Wisconsin
- On May 12, 2000, a supercell with hail up to baseball size and winds of at least 75 mph, affected 4 east central Wisconsin Counties. Total damage was about $122 million
What you can do...
- Know which county you live in or the name of the county you're in. The NWS issues severe thunderstorm warnings on a county basis.
- Monitor a NOAA Weather Radio signal to obtain the latest forecasts and warnings issued by the NWS. Make sure the radio receiver has a battery backup. NWS warnings are broadcast on commercial radio and TV stations, as well as cable TV channels.
- Postpone outdoor activities if the thunderstorms are imminent.
- To protect your motor vehicle or other property from hail damage, try to park it in a garage or car port, or a tent with a strong canvas. If this is not possible, cover the vehicle with old blankets or jackets.
- Don't treat "Severe Thunderstorm Warnings" lightly!!!
...Produced by Warning Coordination Meteorologists from the NWS Offices servicing the state of Wisconsin