The first major cold front of fall is expected to arrive Wednesday in Western Colorado, dropping temperatures to 20 degrees below normal through Friday.
The front will cool down eastern Utah and Western Colorado by Thursday, the National Weather Service said, including single-digit lows in the mountains Friday morning.
In addition to cooler weather, the first significant snow in possible in the high country Wednesday night and Thursday. Freezing temperatures and snowfall likely will affect drivers Thursday morning in high mountain passes, although road temperatures likely will be quite warm in the lower valleys.
A freeze warning that was in effect midnight overnight Sunday expired at 9 a.m. Monday in Southwest Colorado after hitting a low of 25 degrees in Cortez at 4:53 a.m. and 31 degrees in Durango at 6:28 a.m.
The cold front will end the growing season in the Western Slope, the weather service said.
“Frost and freeze conditions will kill crops, other sensitive vegetation and possibly damage unprotected outdoor plumbing,” the weather service said.
In Montezuma County, the overnight low Sunday is expected to reach 31 degrees. Sunny skies were forecast for Monday, with a high of 69 degrees.
The extended forecast for Montezuma and La Plata counties includes overnight lows of 34 degrees on Wednesday, 19 degrees on Thursday, 22 degrees on Friday and 27 degrees on Saturday.
The cold snap this week may fully dress trees in their autumn colors in the San Juan and Las Plata mountains. As of Thursday, the color change hit 60% of peak in the La Platas near Mancos, 75% to 85% from Dolores to Rico, and 75% to 85% from Rico to Telluride.