National Weather Service United States Department of Commerce


A strong upper level low brought an end to record heat, and provided Denver its second earliest measurable snowfall on record. Numerous heat records were set leading up to the snowfall, and several new snowfall and cold records were also broken in this abrupt bout with winter.

On September 5, 2020, Denver set its all time record high for September, reaching 101 degrees during the afternoon. This was also the latest date a 100 degree reading has ever been observed in Denver.  Another daily record high was then tied on September 6 when Denver hit 97 degrees. September 7th was the last day of heat across the eastern plains of Colorado, when Denver's high temperature reached 93.  That tied us for the record for the number of 90 degree days for a year (73), and was also the warmest temperature ever recorded before a day of measurable snowfall.

By the evening of September 7th, a series of cold fronts progressed southward from Wyoming into Colorado, dropping the temperature down to the low 30s by early Tuesday morning. Snow developed across the Front Range and foothills overnight, while a mix of rain and snow developed along the I-25 metro corridor.  A few locations picked up light snow accumulations in the morning. Accumulating snow was mostly confined to the higher elevations much of the day Tuesday, before spreading across the plains during the late afternoon and evening. Snow spread across the far eastern plains overnight, and tapered off by Wednesday morning. 

Total snowfall accumulations were 1 to 3 inches across much of the eastern plains, 3 to 6 inches for cities along the mountains (including Boulder and the western portions of Fort Collins), and 4 to 10 inches for the mountains and foothills of the Front Range. A total of 5.6 inches of snow was measured at the NWS Boulder office, while Denver officially measured a total of 1.0 inches.  


Snow on the NOAA DSRC Campus Tuesday evening
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