Polar vortex to deliver record cold to parts of the U.S.

(NBC News) – Arctic cold is moving across the United States, bringing with it temperatures not seen in at least two decades.

In Chicago, heavy snow Monday morning gave residents a taste of what’s to come. By midweek the high there is forecast to be well below zero, with wind chills as low as 55 below across much of the region.

It’s so cold Lake Michigan has already frozen over along the shoreline, and the is worst yet to come.

Doctors are warning people to be careful.

“I’ve seen people get frostbite within ten minutes of being outside, on their ears, just walking from one place to the next,” says Jeff Schaider of the Cook County Department of Emergency Medicine.

The arctic blast is caused by an extremely cold air mass pushing down from the North Pole.

The Deep South is also bracing for extreme weather. A snowstorm will impact much of the region Tuesday, as Atlanta prepares for Super Bowl 53.