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Hailstorms
Hailstones normally range from the size of a pea to that of a golf ball, but sizes larger than baseballs have
occurred with the most severe storms. Hail tends to fall in swaths that may be 20-115 miles long and 5-30
miles wide. The swath is not normally a large, continuous bombardment of hail, but generally consists of a
series of hail strikes that are produced by individual thunderstorm clouds traversing the same general area.
Hail strikes are typically one-half mile wide and five miles long. They may partially overlap, but often leave
completely undamaged gaps between them. Hailstorms are considered formidable among the weather and
climatic hazards to property and crops of the interior plains of the U.S. because they dent vehicles and
structures, break windows, damage roofs and batter crops to the point that significant agricultural losses
result. Serious injury and loss of human life, however, are rarely associated with hailstorms.
According to the Insurance Information Institute, property insurers pay out an average of $1.5 billion per
year for hail-related losses.
Photo credit: http://www.chaseday.com/hailstones.htm
Ouch!
Iowa Hailstorm Facts...
 Iowa averages 100 hail days per year; however, the vast majority of these
hailstorms are insignificant.
Based on crop-hail data, 50% of the state-wide damage occurs on just the 3
most damaging days of the year.
About half of Iowa’s hail occurs prior to the emergence of summer crops with
greatest crop-hail loss occurring along the Iowa-Nebraska border and the least
occurring along the Iowa-Illinois border.
Overall, crop-hail losses are an average of 5 times greater in extreme western
Iowa than in extreme eastern Iowa.
According to records from the National Climatic Data Center, there were 5,161
hailstorm occurrences between 1950 and 2002. Polk county was the most
affected with 183 reported hailstorms. Warren, Woodbury, Clay, and
Pottawattamie also had high frequency reporting over 100 hailstorms.
Historic Hail Events
Recorded Iowa Hail Events from 1950-2002
Wisconsin Hailstorm Facts...
Roughly 20% 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 72% of all
severe weather events, while tornadoes add up to about 8%.
Any given location in Wisconsin will usually experience about 3 days with hail per year.
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 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.
Wisconsin’s worst and most costly hailstorm took place on May 12, 2000 in a band of storms
south of La Crosse through the Lake Winnebago area to Lake Michigan. Ten counties were
pounded with hailstones 1-3 inches in diameter during the morning hours. Thirty-six people
were injured and the estimated property damaged totaled $121 million.
Source: Data from http://emergencymanagement.wi.gov
Historic Hail Events
Recorded Wisconsin Hail Events from 1982-2001
Regional Variations
States have different levels of tornado and hailstorm
activity.
Different indications: tornado count, hailstorm count,
Crop experience, ISO EC loss costs; are not consistent
Historical losses within states shows variability, as well.
Some is systematic.
But, how credible??
Crop Hail Rates – Corn
Relative to Overall average = 1.00
Crop Hail Rates – Soybean
Relative to Overall average = 1.00
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