Subfreezing temperatures across much of the U.S. left millions of Americans facing dangerous cold as Arctic storms left four dead and knocked out electricity to tens of thousands in the Northwest, brought snow to the South, and walloped the Northeast with blizzard conditions that forced the postponement of an NFL game.

An estimated 95 million people nationwide faced weather warnings or advisories Sunday for wind chills below zero Fahrenheit (minus 17 Celsius). Forecasters said the severe cold was expected to push as far south as northern Texas while the bitter blast sends wind chill readings as low as minus 70 degrees (minus 56 Celsius) in Montana and the Dakotas.

“It takes a matter of minutes for frostbite to set in,” the South Dakota Department of Public Safety said in a statement Sunday urging people to stay indoors.