Frost/Freeze in San Juan River Basin, Colorado

Six of the seven stations available for verification purposes recorded temperatures at or below 32F for at least three hours on the night of October 20th to the 21st. Th lowest recorded temperature was 30F, while the lowest recorded temperature from a RAWS station was 31F. Freezing temperatures lasted on average 5 hours, with the maximum being 11 hours and the minimum being 0 hours. No temperatures below 28F were recorded for any length of time, making this not a season ending freeze.

A storm system moved through on the afternoon of the October 20th, bringing mountain snow and some colder air in its wake. Areas around the Four Corners and the adjacent southwest Colorado valleys cleared out the fasted in the wake of this low, allowing for good radiational cooling on the night of the 20th into the 21st, resulting in a freeze for some areas, though not season ending.