CHICAGO: The eastern half of the U.S. shivered Monday as a dangerously cold whirlpool of dense air known as a "polar vortex" threatened to break decades-old records and freeze exposed skin within minutes.
The bitter weather comes after a heavy snowstorm hit much of the region last week. Officials closed schools in Chicago and other Midwest cities and warned residents to stay indoors.
More than 1,000 flights were canceled Sunday at airports throughout the Midwest.
"It's just a dangerous cold," said National Weather Service meteorologist Butch Dye.
The forecast is extreme: 32 degrees below zero Fahrenheit (-35 Celsius) in North Dakota, and 15 below zero (-26 Celsius) in Minneapolis, Indianapolis and Chicago. Wind chills - what it feels like when high winds are factored into the temperature - could drop into the minus 50s and 60s Fahrenheit (-45 to -51 Celsius).
It hasn't been this cold for almost two decades in many parts of the country. Frostbite and hypothermia can set in within minutes.
"I have seen frostbite occur through clothing," said Douglas Brunette, an emergency room doctor in Minneapolis. "It's not enough just to be covered. You need clothes made for the elements. You need to repel the wind."
The Indianapolis mayor upgraded the city's travel emergency level to "red," making it illegal for anyone to drive except for emergencies or seeking shelter. The last time the city issued such a travel warning was 1978.
Many cities came to a virtual standstill. School was called off Monday for the state of Minnesota. Government offices and courts in several states closed.
Southern states were bracing for possible record cold temperatures, too. With two freezing nights ahead, Louisiana citrus farmers could lose any fruit they cannot pick in time.