Summer came to an abrupt end in the Rockies on Tuesday as cold air from Canada caused temperatures to drop by up to 60 degrees (15 Celsius) in less than 24 hours.
The change brought snow to Colorado, a day after people had to flee their homes because of a wildfire that ballooned in hot, windy weather.
Highways in Wyoming including portions of Interstate 80 began closing as snow picked up across the state, where forecasters predicted up to a foot (30 centimeters) of snow in the mountains and temperatures in the teens (-7 Celsius) overnight.
Strong winds knocked out power in northern Utah, where temperatures dropped by 40 degrees.
Six inches or more of snow could fall in the northern and central Rockies, with 1 to 2 feet dropping in the highest peaks, the National Weather Service said. It has issued scattered winter storm warnings and weather advisories from southern Montana to southern Colorado. Freeze and frost warnings were also posted for parts of Montana, Idaho, Colorado, Nebraska, North Dakota and Minnesota.
The cold and snow will help the fight against the Cameron Peak Fire in northern Colorado nearly quadrupled in size over the weekend, sending smoke and ash to the Denver area.