Hail Climatology
What areas have the most hail?
Though Florida has the most thunderstorms, Nebraska, Colorado, and Wyoming usually have the most hail storms. The area where these three states meet – "hail alley," averages seven to nine hail days per year. The reason why this area gets so much hail is that the freezing levels (the area of the atmosphere at 32 degrees or less) in the high plains are much closer to the ground than they are at sea level, where hail has plenty of time to melt before reaching the ground. Other parts of the world that have damaging hailstorms include China, Russia, India and northern Italy.
When viewed from the air, it is evident that hail falls in paths known as hail swaths. They can range in size from a few acres to an area 10 miles wide and 100 miles long. Piles of hail in hail swaths have been so deep, a snow plow was required to remove them, and occasionally, hail drifts have been reported.
How harge can hail get?
The largest hailstone recovered in the U.S. fell in Aurora, NE on June 22, 2003 with a diameter of 7 inches and a circumference of 18.75 inches.
» More About GIANT HAIL PROBABILITIES
Estimating Hail Size
Hail size is estimated by comparing it to a known object. Most hail storms are made up of a mix of sizes, and only the very largest hail stones pose serious risk to people caught in the open.
- Pea = 1/4 inch diameter
- Marble/mothball = 1/2 inch diameter
- Dime/Penny = 3/4 inch diameter - hail penny size or larger is considered severe
- Nickel = 7/8 inch
- Quarter = 1 inch
- Ping-Pong Ball = 1 1/2 inch
- Golf Ball = 1 3/4 inches
- Tennis Ball = 2 1/2 inches
- Baseball = 2 3/4 inches
- Tea cup = 3 inches
- Grapefruit = 4 inches
- Softball = 4 1/2 inches
HOW DOES NSSL CONTRIBUTE?
A recent study by one of NSSL's scientists used data from 1980 to 1995 to estimate the daily climatological probability of severe weather from thunderstorms – including tornadoes, damaging winds, and large hail – occurring within 25 miles of any location in the U.S.
SHAVE – The Severe Hail Verification Experiment was conducted over the summer of 2006 to enhance climatological information about hail in the U.S.