Temperatures in parts of the US could drop to about -30C as Donald Trump urged voters in one state to brave the blizzard conditions.
At least four people have died in a dangerous Arctic blast, which has knocked out electricity for hundreds of thousands of people, brought snow even to southern states and postponed a key NFL match.
Wind chills in Montana and the Dakotas have felt as low as -57C, while temperatures could be 20-40 degrees lower than normal in large parts of the country between Idaho and Ohio.
“To highlight just how intense this outbreak of Arctic air is, over 95 million citizens fall within a Wind Chill Warning, Advisory, or Watch,” the US National Weather Service (NWS) said.
In Iowa, where it could feel as cold as -40C in the wind, the blizzard forced a pause in campaigning events as Republicans prepare for the party’s first nominating contest on Monday.
But Mr Trump – the runaway favourite to win the Republican nomination – told supporters “you can’t sit at home” and that voting would be “worth it”, even as piles of snow cover campaign banners and cars were left abandoned.
“If you’re sick as a dog, you say, ‘darling, even if you vote and then pass away, it’s worth it’,” he said, making up a conversation between partners and joking voters may even meet their future spouse.
“Remember, if you’re sick, if you’re just so sick, you can’t, ‘darling, I don’t think’… get up.”
In such extreme conditions, frostbite can take just minutes to set in.
The weather forced the NFL to postpone the Pittsburgh Steelers versus Buffalo Bills playoff game hosted in bone-chilling Buffalo, New York, where at least two feet of snow has fallen.
Snow, sleet and freezing rain could hit Texas, Arkansas, Louisiana and the Southern Appalachians early this week, with even Atlanta experiencing -10C by Wednesday.
The extreme weather is a reminder of the February 2021 freeze that left millions in Texas and other central states without power, water and heat for days.
Read more:
It might take more than a storm to knock Trump off course
What are caucuses and why is the one in Iowa so important?
The Texas power grid operator, ERCOT, appealed to the public on Sunday to conserve electricity amid “record-breaking demand”.
Meanwhile, Maine, in the northeast of the country, saw historic flooding up and down the entire coast, with floods in Portland Harbor reaching 14.57 feet and sweeping away small buildings.