DENVER (AP) – Wind chills down to around 50 below zero are possible in the Rockies as bitter cold arctic air hangs over the region.

Colorado’s Eastern Plains, including Colorado Springs, could see wind chills over 25 to 35 below zero from Tuesday night into Wednesday. In southern Wyoming, the National Weather Service says a few locations in the Laramie Valley could feel as cold as 50 below zero with the wind. Elsewhere the temperature will feel like 20 to 35 below.

Sub-zero temperatures covered nearly all of Montana Tuesday morning, with a wind chill as low as 45 below at Monarch southeast of Great Falls.

Temperatures are expected to rise all the way into the 20s for New Year’s Eve.

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