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

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

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

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 weather.com. 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.]

More than 50 million people will be affected

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.]