The polar vortex flooding into the US is set to deliver the coldest air on Earth to the northern half of the country, threatening millions with more dangerous winter conditions.

Both snow and bitterly cold winds are set to move across the Midwest and Northeast this week, triggering official warnings from Montana and the Dakotas to New York, Pennsylvania, and the New England states today.

The National Weather Service (NWS) issued winter weather advisories in 17 states on Wednesday, and forecasters compared the cold air moving down from Canada and Greenland to a ‘wrecking ball.’

The polar vortex, which floods into the US when the stable stream of cold air over the North Pole weakens, will send December highs that are normally in the 30s or 40s dropping by as much as 30 degrees by this weekend.

Weather Trader meteorologist Ryan Maue said the Arctic blast was a ’textbook ‘Polar Vortex’ mega-dump of western Canadian cold pool,’ adding that Minneapolis and Chicago could see temperatures fall 40 degrees below normal averages by Sunday.

Wind chills in the Dakotas could reach -45°F, while Chicago is expecting -20°F wind chills, and New York City will struggle to climb out of the 20s for their daily highs.

Meanwhile, AccuWeather has predicted more snowfall through Wednesday night in North Dakota, Minnesota, Wisconsin, Michigan, Pennsylvania, New York, Vermont, New Hampshire, and Maine. Some isolated areas could see up to 12 inches.

Around Chicago, Milwaukee, Detroit, and Cleveland, Americans should expect to see a messy mix of snow, sleet, freezing rain, and ice that could make roads hazardous between Wednesday and Thursday.

Major cities from Chicago to New York City (Pictured) could see bitter cold temperatures this week, falling up to 30 degrees below historical averages

Meteorologists have warned that multiple Alberta clipper storms will bring snow to the Midwest and Northeast through this weekend

The prolonged Arctic conditions have been blanketing the northern half of the US since the first week of December, and meteorologists have predicted that multiple waves of cold air will keep flooding into the country through next week.

The polar vortex is like a giant, spinning whirlpool of cold air high up in the atmosphere above the North Pole, normally held in place by strong winds that act as a barrier, keeping the extreme cold locked away in Greenland and Canada.

However, strong storms and high-pressure systems in the lower atmosphere have sent ripples of warmer air upward that knocked this vortex off balance, allowing the icy air to plunge south and send the US into a deep freeze.

That cold air from the north has been colliding with warmer air moving north from the Gulf Coast, creating the perfect conditions to create rain and sleet in the South and heavy snow everywhere north of Missouri this month.

Climatologist Judah Cohen, a research scientist at MIT, told USA TODAY: ‘Some of the coldest, if not the coldest, temperatures across the entire globe will cover the central and eastern US over the weekend and into early next week.’

AccuWeather meteorologists added that this weekend’s frigid forecast could be the best chance for major cities such as New York, Boston, and Philadelphia to see significant snowfall.

However, forecasters warned that the fast-moving system may also lead to widespread travel disruptions throughout the Northeast and dangerous driving conditions for anyone in the Plains, Midwest, and Ohio Valley.

AccuWeather Meteorologist Brandon Buckingham warned: ‘Fast-moving snow squalls moving across interstates can rapidly reduce visibility and coat the asphalt in a matter of minutes, creating dangerous driving conditions.’

More snow and freezing temperatures are expected to come next week, as the polar vortex collapse lasts through December

Wind chills in the US and Canada are expected to fall well below zero, with northern Canada seeing life-threatening winter conditions

In Canada, Maue revealed that the early winter chill has been even more severe, with wind chills in the country’s northern territories reaching a staggering -80°F, which the meteorologist compared to a ‘cryogenic deep freeze.’

AccuWeather noted that the ongoing waves of bitter cold air from Canada are being carried by Alberta clippers, fast-moving winter storms that form in western Canada and race southeast across the US.

They bring quick bursts of snow, strong winds, and sharp cold.

These clippers are directly tied to the ongoing polar vortex collapse, as the cold air moving down from Canada spawns these storms as they collide with the milder air over the US.

Each clipper lasts only one to two days, but forecasts predict that a series of them will keep hitting through this weekend, with the coldest air peaking on Monday.