CAMBRIDGE, Mass. — The polar vortex is bringing dangerously low temperatures to a wide swath of the Midwest, forcing schools and universities to close and leadingthe governors of Illinois, Michigan and Wisconsin to declareemergencies.

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

The high on Wednesday in Des Moines 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 Fairbanks, Alaska, will also be warmer during the day on Wednesday than Des Moines, with a high of 4 degrees.

[Read cold weather tips from Chicagoans.]

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

[Read more about how it’s possible that such a cold snap can occur during a period of climate change.]

With wind chills in Minneapolis-St. Paul expected to be as low asminus 45 tominus 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.

[Read about the signs of frostbite.]