A very cold air mass will penetrate the Northwest this weekend, and it will remain extremely cold into next week. Montana will feel the worst of it with temperatures dropping into the teens and single digits Sunday, then subzero weather is likely at night.

Washington, Oregon and Idaho will also feel the sting of this bone-chilling air mass. In Spokane, for instance, highs will be in the middle 20s Sunday and Monday, and overnight lows will be in the single digits. The cold pockets of eastern Washington, eastern Oregon and northern Idaho will drop below zero both Sunday and Monday nights.

The invasion of cold air will not trigger a snowstorm, but light amounts of snow are expected from Alberta to Wyoming.

Story By AccuWeather.com Senior Meteorologist John Kocet.