The National Weather Service predicts at least 6 inches (15 centimeters) of snow from the Colorado high country through most of Wyoming, where winter storm warnings are in effect.
More than a foot of snow (30 centimeters) could fall in some mountainous areas.
The forecast Monday and Tuesday also calls for gusty winds in much of Wyoming and western Montana. That means wind chills as much as 30 degrees below zero (-34 Celsius).
Butte has already broken record cold temperatures this morning with a low of -26. Kalispell also broke a record from 1936 with a low of -16!
Yesterday, Butte’s temperature, -27 and -35 with the wind chill was colder than Antarctica.
Billings schools and several other Eastern Montana school districts are closed today because of the weather.
Forecasters urge people who must drive to bring an extra flashlight and food in water in case they get stuck.