A blast of arctic air is set to bring life-threatening cold to the U.S. Midwest and Northeast this week.

Meteorologists say a polar vortex will envelop a quarter of the country in sub-zero cold.

In Chicago, temperatures are expected to hit an astounding 25-below-zero by midweek.

And wind chills could dip as low as 55-below-zero.

A major snowstorm has already pounded parts of the Midwest.

Whiteout conditions caused multiple crashes on Interstate 90 in Pennsylvania over the weekend.

And in Wisconsin, day one of the Wausau Snowmobile race was cancelled because of the bitter cold.

SOUNDBITE: RALPH MERWIN, RACE PRESIDENT, SAYING: "We had tremendous cold temperatures and snow dust and the drivers could not see, where they were going." As the deep freeze sets in, meteorologists say Chicago and Minneapolis will be colder than in parts of the Arctic.