The coldest air in at least 25 years is pouring into the Midwest on Wednesday, promising to topple records and prompting officials to warn of "life-threatening" temperatures.

The wind chill is down to minus-60 degrees in Minnesota, while Chicago is looking at one of its coldest days in city history. Nearly 90 million people will endure conditions below zero degrees this week from this polar vortex cold snap, according to the National Weather Service, and 25 million of those will face temperatures below minus-20.

Photo gallery at end of story: See photos across the country as frigid temps and wintry weather blanket much of the U.S.

In northern Minnesota, where the coldest temperatures have been reported, the wind chill sank to minus-65 degrees in Hubbard County around 7 a.m., the lowest observed thus far.

After plunging to minus-23 Wednesday morning with a wind chill around minus-50, Chicago's afternoon temperature on Wednesday doesn't seem likely to climb above minus-14 degrees Wednesday afternoon. That would have been a record for the coldest maximum temperature ever reported at Chicago O'Hare International. However, just after midnight on Wednesday, the temperature was still minus-10, a degree above the coldest high ever recorded of minus-11, most recently on Jan. 18, 1994.

If you take an average of the high temperature for the day (minus-10, which occurred at midnight) and low temperature (minus-23), it is likely to be Chicago's second coldest day on record, only trailing Dec. 24, 1983.

"[T]he message is to avoid outdoors if one can and if not, this is the day to dress as absolutely warm as possible," the Weather Service office serving Chicago wrote. It called the wind chills in northern Illinois "about as frigid and dangerous ... as can be."

After this historically cold day, Thursday morning lows will plummet close to the city's all-time record low temperature of minus-27, set on Jan. 20, 1985.

The state record in Illinois is also in jeopardy - minus-36 degrees set in Congerville on Jan. 5, 1999. Conditions are particularly favorable for state records to fall this week, with clear skies and fresh snow on the ground.

The cold air is riding behind an Arctic front that brought several inches of snow to the same region over the weekend. The pure white ground will enhance the chill, as sunlight reflects off the snow and back to space instead of being absorbed into the ground where it could warm things up. If those conditions line up, they could "easily push" temperatures to minus-35 to minus-39 in northern Illinois, the National Weather Service said Tuesday, which would jeopardize if not topple the state's coldest low.

Several records for Jan. 30 were broken at sunrise, including two set in 1966 in Northern Illinois: Chicago's record of minus-15 and Rockford's at minus-19. The temperature in both of those cities was around minus-20 and still falling Wednesday morning.

Other all-time records in jeopardy this week:

Rockford, Illinois - Minus-27 set on Jan. 10, 1982

Cedar Rapids, Iowa - Minus-29 set on Jan. 15, 2009

Dubuque, Iowa - Minus-32 set on Jan. 7, 1887

Moline, Illinois - Minus-28 set on Feb. 3, 1996

While actual temperatures drop to negative double digits this week, media have been clamoring to find exotic locations that will be warmer than the Midwest. Antarctica, for example, will be a balmy 10 degrees Thursday morning when Minneapolis drops to around minus-30. But it is summertime in the Antarctic, so that shouldn't be surprising. What is surprising, at least meteorologically, is that the Midwest will be colder than the North Slope of Alaska on Thursday morning. Utqiagvik, formerly known as Barrow, will drop to around minus-20 - 10 degrees warmer than parts of Minnesota, Wisconsin and Illinois are expected to be at the same time.

Even if all-time records are not broken, the National Weather Service in Chicago is calling this week's forecast "life-threatening extreme cold" that "can lead to rapid onset of frostbite and hypothermia." A recent report from the Centers for Disease Control and Prevention found that cold weather is responsible for the majority of weather-related fatalities.

The wind chill temperature is more than a catchy forecast term. The wind blows away the insulating layer of warm air around us generated naturally by our bodies. Wind chill attempts to quantify the effect in terms of how it feels on our skin, which is why you'll sometimes hear it called the "feels like" temperature. A wind chill of minus-20 degrees can cause frostbite in as little as 30 minutes.

Dozens of records could be broken this week as the temperatures fall. Forecasts suggest that Wednesday's high temperatures in the Midwest might be some of the coldest on record for certain locations, and Thursday morning's low temperatures could also set new records.


Photos: Deep freeze blankets parts of U.S.

Photos from the Midwest and other parts of the U.S. as frigid temps and snow impacted many regions Tuesday and into Wednesday:

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