The North Pole is surrounded by a massive circular upper-air weather phenomenon in the Arctic called the polar vortex. It is a typical pattern that tends to contain the coldest weather close to the North Pole and is more pronounced in the winter.

Meteorologists warn that a stretched polar vortex could bring severe winter weather to much of the United States.

An unusually brutal winter storm is set to pummel more than 160 million Americans from Friday, as a stretched "polar vortex" sends a devastating blast of Arctic air, bringing heavy snows and freezing rains.

What travelers should know as a polar vortex heads towards the United States, including how airlines and hotels are responding, and experts on whether you should cancel your trip.

Here’s the wind chill chart. Notice the four shadings, indicating how long it will take for frostbite. When we get to wind chills of -35 degrees or colder, frostbite can occur in just 10 minutes. Even in the “not as cold” areas of lower Michigan we could get frostbite within 30 minutes.

The brief respite of a January thaw is over as a significant pattern shift readies a return to harsh winter conditions across the Midwest and Northeast. Meteorologists are tracking a southward dip in the jet stream that will funnel rounds of Arctic air and multiple waves of snow into the Great Lakes and New England starting mid-week.