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Hail occurs frequently in parts of Colorado, especially east of the mountains. Most stones are less than 5/8" diameter. But each year a few storms produce stones of exceptional size. We might see a very large hail stone and wonder, could this be the "new" record size stone for the state of Colorado. It just might be.

This guide will give you some very helpful instructions on what to do if you think that you might have a record size hailstone. There are certain criteria that are used nationaly for measuring and preserving the stone so that it can be verified.



The following pdf contains a set of guidelines recomended from the State Climate Extremes Committee (SCEC).


LARGEST RECORDED HAILSTONES FOR COLORADO (Based on NOAA Storm Data Reports through April 2012)

4.5" June 9, 1971 Kit Carson County
4.5" June 22, 1979 Morgan County
4.5" July 30, 1979 Larimer County

4.5" June 4, 1983 Weld County
4.5" June 12, 1983 Washington County
4.5" August 2, 1983 Denver County
4.5" June 23, 1987 Otero County
4.5" July 9, 1987 Sedgwick County
4.5" June 29, 1989 Cheyenne County
4.5" June 30, 1989 Morgan County

4.5" July 6, 1993 Washington County
4.5" June 7, 1994 Yuma County
4.5" May 22, 1996 Sedgwick County
4.5" July 23, 1996 Elbert County
4.5" October 11, 1997 Bent County

4.5" July 5, 2000 Logan County
4.5" May 17 2001 Baca County
4.5" August 17, 2002 Washington County
4.5" August 9, 2004 El Paso County

4.5" July 13, 2011 Adams County



Think you found a record size hailstone? Here are seven things you should do right away:

1) First item is to report severe weather ASAP to your National Weather Service office or Law Enforcement agency:

NE Colorado Northern Front Range - Boulder NWS Office (303) 494-4221
SE Colorado and Southern Front Range - Pueblo NWS Office (719) 948-9429
Yuma, Kit Carson, Cheyenne counties - Goodland, Kansas NWS Office (785) 899-7119
Western Colorado - Grand Junction, NWS Office: (970) 243-7007

-Then, when the coast is clear . . . .

2) Handle the stone as little as possible. Photograph the stone untouched in the environment where you found it. Include in the photo the other stones that landed nearby. Then separately photograph the stone with a ruler held directly beside or below the stone. if possible place an object of familiar size in the photo beside the hail stone -- a baseball, golfball, etc. Photos of hail damage are also appreciated.

3) Carefully measure the greatest length (diameter) and girth (circumference) of the stone and photograph the measurement.

4) If an accurate scale is available, weigh the stone to the nearest gram or nearest 1/16 ounce.

5) Preserve the stone immediately in a sealed ziplock bag. If bag is not available or not big enough, use clear plastic wrap. Promptly place in your freezer.

6) Contact the Colorado Climate Center: 970-491-3690

7) If you are a CoCoRaHS observer, please submit a "Real Time" Hail Report


Guide for hailstone size (diameter measurement listed)
Ping pong ball – 1.5 inches
Golf ball –1.75 inches
Tennis ball - 2.5 inches
Baseball - 2.75 inches
Hockey puck- 3 inches
Softball - 4 inches
Grapefruit - 4.5 inches
CD/DVD - 4.75 inches


Resources and Publications:

Hail, Hail, Hail! The Summertime Hazard of Eastern Colorado
Origins of Hail
Overview of the National Hail Research Experiment (NHRE)


Questions? Contact the Colorado Climate Center here: Contact Us