Flash floods aren't just for places that typically get heavy rainfall. And sometimes hail combines with torrential rain to leave behind a real mess.
On Aug. 1, 1985, 40 years ago this evening, a cluster of slow-moving severe thunderstorms dumped up to 7 to 8 inches of rain in just 3 hours over Cheyenne, Wyoming, triggering major flash flooding throughout the city.
Twelve people were killed, mostly in vehicles swept away trying to cross flooded streets along Dry Creek, according to the National Weather Service.
Flooding also occurred along Crow Creek and throughout the downtown area. Several city and state government buildings suffered significant flood damage.
If that wasn't enough, a foot of hail up to the size of limes pelted the city, then was swept by the floodwater into drifts as high as 3 to 6 feet, resembling a winter storm in early August. Those huge hail piles didn't disappear until two days after the storm.
The storm's $65 million price tag was Wyoming's most damaging flash flood.
Cheyenne set all-time Wyoming records for 24-hour (6.06 inches) and 1-hour (3.5 inches) rainfall. These were off the chart rain rates for a semi-arid High Plains climate where their average annual precipitation is only 15.41 inches.
Jonathan Erdman is a senior meteorologist at weather.com and has been covering national and international weather since 1996. Extreme and bizarre weather are his favorite topics. Reach out to him on Bluesky, X (formerly Twitter) and Facebook.
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