Residents of the Midwestern US are braced for the coldest weather in two decades, with forecasters warning that the temperatures would be life-threatening.
Icy conditions snarled travel across the region and thousands of flights were cancelled or delayed.
Days after the northeast was hammered by the first winter storm of the season, some officials pre-emptively closed schools and a plane skidded off a runway into snow in New York.
The US National Weather Service said: "The coldest temperatures in almost two decades will spread into the northern and central US today behind an Arctic cold front."
It said: "Combined with gusty winds, these temperatures will result in life-threatening wind chill values as low as -51 Celsius."
In weather that cold, frostbite can set in on uncovered skin in a matter of minutes, experts warned.
Elsewhere in the midwest, forecasters warned that Chicago and Indianapolis could see overnight lows of -24C, Minneapolis -34C and -35C in Fargo, North Dakota.
The coldest temperature reported in the lower 48 states today was -38C in Crane Lake, Minnesota.
The northeast was forecast to see a brief thaw before intense cold returns late tomorrow.
About half of all flights arriving and departing Chicago O'Hare International Airport were cancelled today, according to Flight Aware, which tracks flight statistics.
Nationwide, about 2,855 flights had been delayed nationwide by midday and 2,332 had been cancelled.
In New York City, John F Kennedy International Airport was closed for a couple of hours this morning after a Bombardier jet skidded off a taxiway soon after landing.
The Delta Connection flight had landed safely after arriving from Toronto with 35 passengers on board, the Port Authority of New York & New Jersey, which runs the airport, said.
Officials in several states asked residents to use extra precautions when outdoors.
Minnesota Governor Mark Dayton ordered all public schools in the state closed tomorrow to protect children from dangerously cold weather.
Chicago schools will be open tomorrow despite the cold, but officials advised parents to "use their own discretion in deciding whether to send their child to school".
Between 15-30cm of snow was predicted from Chicago to Detroit, AccuWeather said, while icy sleet and rain was forecast for much of the northeast.