Record-low temperature records could fall as US braces for dangerous 'polar vortex' conditions

A man spreads salt on icy sidewalk in Chicago, Friday, Jan. 3, 2014. The snowstorm may finally have left town but a winter weather advisory is in effect for this evening when southerly winds are expected to kick up blizzard-like conditions. (AP Photo/Nam Y. Huh) (The Associated Press)

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Ice floats on the surface of Lake Michigan Friday, Jan. 3, 2014, in Chicago. Single-digit temperatures are hitting Illinois after the state was blanketed in snow. Meanwhile, residents are bracing for a deep freeze. Highs early next week likely won't reach zero and wind chills could sink to 45 below. (AP Photo/M. Spencer Green) (The Associated Press)

Sledding enthusiasts take to Cricket Hill at Montrose Beach Park Friday, Jan. 3, 2014, in Chicago. Single-digit temperatures are hitting Illinois after the state was blanketed in snow. Meanwhile, residents are bracing for a deep freeze. Highs early next week likely won't reach zero and wind chills could sink to 45 below. (AP Photo/Charles Rex Arbogast) (The Associated Press)

SIOUX FALLS, S.D. – It has been decades since parts of the Midwest experienced a deep freeze like the one expected to arrive this weekend.

Potential record-low temperatures starting Sunday and expanding into next week are increasing fears of frostbite and hypothermia even in a region where residents are accustomed to bundling up.

This "polar vortex," as one meteorologist calls it, is caused by a counterclockwise-rotating pool of cold, dense air. The frigid air, piled up at the North Pole, will be pushed down to the U.S., funneling it as far south as the Gulf Coast.

Temperatures are projected to dip to 25 below in Fargo, N.D., and minus 31 in International Falls, Minn. The San Francisco-Green Bay playoff game Sunday at Lambeau Field could be one of the coldest NFL games ever played.