Bone-chilling temperatures caused by a "polar vortex" enveloped the nation's midsection Monday, with record lows closing schools, forcing the cancellation of thousands of flights and even freezing the engines of an Amtrak train for nine hours.
The icy blast — described by meteorologists as the worst in decades — is set to bring below-zero temperatures to more than half of the continental U.S. on Monday and Tuesday as it spreads east and south.
The Midwest and Plains have already endured temperatures as low as minus 30 degrees and wind chills that feel like minus 50 degrees.
A man shovels snow following a snow storm that left up to 8 inches of snow on January 3, 2014 in New York.Getty Images
Anyone venturing outside without wrapping up risked frost bite "in minutes or even seconds," according to Kevin Roth, lead meteorologist at The Weather Channel.
Illinois Gov. Pat Quinn urged people to avoid venturing outside unless absolutely necessary and to dress appropriately should they need to go out.
"This winter storm will be one for the record books and we want to make sure everyone stays safe and warm until it passes," he said in a statement Sunday night.
More from NBC News:
'Only getting colder': Blast of frigid air set to smash records
Out of the blizzard, into the icebox; low temperature records may be shattered
Dangerous cold snap: 10 things to know
Passengers on an Amtrak train from Detroit to Chicago were stranded for more than nine hours after both the train's engines froze.