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It'll be a cold snap for the ages — the Ice Ages!

The East, the Midwest and even the Deep South, are bracing for a once-in-a-generation arctic blast that is forecast to leave 75 million Americans shivering in subzero temperatures, meteorologists said Tuesday.

By the end of Wednesday, 85 percent of the U.S. land area and 230 million Americans will experience temperatures of 32 degrees or colder, thanks to this extended polar vortex.

And 25 percent of America will get down to 0 degrees in dangerous cold that will touch 75 million U.S. residents.

"Historic cold, unprecedented cold, these are all adjectives you could use to describe this," NBC meteorologist Kathryn Prociv said.

This arctic blast will surely freeze the texting thumbs of younger Americans.

"These are some of the coldest temperatures an entire generation has ever felt, talking about the millennials," Prociv said. "A lot of these temperatures will be the coldest since about 1994, when a lot of them were just being born."

The mercury was expected to dip to minus-22 Wednesday in Chicago, where it hasn't been minus-20 since Jan. 18, 1994. If Chicago hits minus-22, it would be as cold as the South Pole and colder than Siberia and Barrow, Alaska — the northernmost point of the United States.

Milwaukee was bracing for an overnight low of about minus-28 degrees, which would threaten Brew Town's all-time low of minus-26, set in 1996.

Des Moines, Iowa, could see the mercury drop to minus-21 early Wednesday in potentially the coldest day there since it was minus-20 on Feb. 4, 1996.

The low temperature in Philadelphia was forecast to be 5 degrees on Wednesday.

Snow was expected set fall in Buffalo, New York, on Tuesday night, for 24 to 96 hours, dumping 12 to 24 inches.

A dusting of snow even fell on Alabama on Tuesday, as Gov. Kay Ivey declared a state of emergency for this week's cold weather.

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Shelters and churches in places such as Chicago, Detroit, and Ann Arbor, Michigan, encouraged the homeless to find refuge from the harsh weather.

Chicago Mayor Rahm Emanuel said Tuesday that the city was turning five buses into makeshift warming centers moving around the city, some with nurses aboard.

Cristina Villarreal, a spokeswoman for the city's Department of Family and Support Services, said: "We're bringing the warming shelters to them so they can stay near all of their stuff and still warm up."

The upper Midwest temperatures were expected to be so cold that even brief exposure could be dangerous.

"You're talking about frostbite and hypothermia issues very quickly, like in a matter of minutes, maybe seconds," said Brian Hurley, a meteorologist with the National Weather Service's Weather Prediction Center.

The U.S. Postal Service said it would suspend delivery services on Wednesday in Minnesota, western Wisconsin, Iowa and western Illinois. There will also be no mail or package pickups, it said.

Driving was treacherous throughout the region. In western Michigan, several multicar pile-ups occurred on Tuesday, NBC affiliate WOOD reported, while two semi-trailers were involved in a massive crash in Gaines Township, the Dutton Fire Department said.

Public schools in Cleveland, Minneapolis, Milwaukee, Buffalo, Detroit and Chicago canceled classes through at least Wednesday.

"We are monitoring the forecast for Thursday and will notify families and staff of closures by late Wednesday afternoon," Minneapolis Public Schools said in a statement.

In Kentucky, Gov. Matt Bevin wasn't happy about dozens of districts' decisions to cancel Wednesday's classes, saying in an interview with WHAS radio of Louisville: "We're getting soft."

"Now we cancel school for cold," Bevin told Terry Meiners, the host. "I mean, there's no ice going with it or any snow. What happens to America? We're getting soft, Terry. We're getting soft."

Bevins said that he was being "only slightly facetious" and that he had a real concern — "that in America, on this and any number of other fronts, we're sending messages to our young people that if life is hard, you can curl up in the fetal position somewhere in a warm place and just wait 'til it stops being hard. And that just isn't reality."

(You can listen to the entire interview here.)

Major universities across the Midwest have also called off classes for Wednesday, including:

The University of South Dakota, the University of North Dakota, Cleveland State University, the University of Iowa, Iowa State University, the University of Wisconsin, the University of Notre Dame, Northern Illinois University, the University of Illinois, the University of Illinois at Chicago, the University of Michigan, Michigan State University, the University of Wisconsin, the University of Wisconsin-Milwaukee, Northwestern University, Purdue University, the University of Minnesota and Canisius College in Buffalo.