CHICAGO (AP) - Temperatures not seen in years are likely to set records in the coming days across the Midwest, Northeast and South.
A "polar vortex" air mass will affect nearly half of the continental U.S. starting Sunday and into Monday and Tuesday, with wind chill warnings stretching from Montana to Alabama.
The bitterly cold temperatures already pushed into northern states Sunday morning. The National Weather Service reported a temperature of 9 below zero in Bismarck, N.D., and negative 21 at Duluth, Minn.
Snow preceded the polar air from Michigan to Kentucky. Forecasts called for up to a foot in eastern Missouri and parts of central Illinois.
Frostbite and hypothermia can set in quickly at 15 to 30 below zero. Medical experts say people should wear hats, face protection and layers of clothing.