One nice feature of the Plains winter is that cold weather can be replaced by unexpectedly mild weather. The most dramatic of these changes are brought on by a chinook. This is the name given to the foehn wind on the eastern side of the Rockies. The chinook generally blows from the southwest, but that can vary by terrain. After an intense cold spell, a chinook can raise temperatures by 20 to 40 degrees Fahrenheit in just 15 minutes. Havre, Montana saw temperatures jump from 11 °F to 42 °F in just 3 minutes! After the first warmup, temperatures might fluctuate wildly as patches of warm or cold air gain influence. But the most important effect of the chinook is its ability to melt and evaporate snow. A foot of snow may disappear in a few hours. That’s the reason the chinook is also known as the “snow eater”.
Mary Knapp, Weather Data Library