Here are some of the salient facts about this brutal cold front.

— The Midwest will be colder Wednesday than parts of Antarctica and Alaska.

The high Wednesday in Des Moines, Iowa, will be a bitter minus 10 degrees Fahrenheit. Wednesday’s high at McMurdo Station in Antarctica will be a comparatively mild 17 degrees, according to weather.com. Fairbanks, Alaska, will also be warmer during the day Wednesday than Des Moines, with a high of 4 degrees.

— More than 50 million people will be affected

A large expanse, from the Dakotas to western Pennsylvania, are under wind chill warnings or advisories from the National Weather Service.

— You could get frostbite in five minutes.

With wind chills in Minneapolis-St. Paul expected to be as low as minus 45 to minus 65 degrees from Tuesday night through Thursday morning, the National Weather Service is warning people that any exposed skin could get frostbite in as little as five minutes.

— The last time Chicago faced temperatures this low was more than 30 years ago.

The predicted low in Chicago on Wednesday night is minus 26 degrees Fahrenheit. According to the National Weather Service, the last time it was that cold in Chicago was Jan. 20, 1985, when Chicago set its low temperature record of minus 27 degrees. With the wind chill, it could feel like minus 55.

— Thousands of flights are being canceled.

On Monday, 1,986 flights were canceled across the country, including more than 1,400 that were supposed to fly into or out of Chicago’s O’Hare and Midway airports, according to Flightaware.com. On Tuesday, as of late afternoon, more than 1,800 flights had been canceled, including more than 500 into or out of Chicago. Around half of the flights into and out of Midway were canceled Tuesday.

— Hundreds of schools are being closed.

Detroit and Milwaukee closed all public schools Tuesday. Minneapolis has closed schools both Tuesday and Wednesday. Chicago Public Schools canceled all after-school activities Tuesday and all classes and activities Wednesday. Many other public, private and parochial schools across the region have closed as well.

— Hundreds of thousands of college students will be hunkering down.

Many colleges across the Midwest have canceled classes during the cold snap, including the University of Wisconsin-Madison, the University of Illinois at Chicago, the University of Chicago, Northwestern University, Michigan State University, the University of Michigan at Ann Arbor, the University of South Dakota and Kent State University.

This article originally appeared in The New York Times.