On the evening of August 1st, 1985, a devastating hailstorm struck the city of the Cheyenne, Wyoming leading to flash flooding across the city. Crow Creek, Dry Creek and the downtown sector were inundated with fast rising water from the storm. The National Weather Service Forecast Office in Cheyenne measured 6.06 inches of rainfall as the official measurement though upwards to 7.87 inches in some places in the city, all in about a 3-hour span! In addition, a one-hour rainfall total of 3.50 inches was recorded setting a new 1-hour record along with the 6.06 inches becoming the new 24-hour record for the state of Wyoming. 

The rainfall was not the only impact felt by the city. Hailstones up to 2 inches in diameter fell with some areas seeing this hail pile up close to 1-foot tall before being swept by wind and water into 3-6 foot drifts. Thunderstorm winds blew at 70 mph. While a few funnel clouds were observed along with two short-lived tornadoes. 

In all, 12 fatalities, 70 injuries, and total damages exceeding $61 million were reported. Most of the deaths were associated with people being swept away in their cars as they tried to cross flooded streets along Dry Creek. 

For more information, please see the Meteorological Analysis of the Cheyenne, Wyoming, Flash Flood and Hailstorm of 1 August 1985

Hail and floodwaters in downtown parking lot in Cheyenne, Wyoming of August 1985

Credit: United States Geological Survey (USGS)