CHICAGO -- The eastern half of the US shivered Monday as a dangerously cold whirlpool of dense air known as a "polar vortex" threatened to break decades-old records.
The far-below-freezing 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 in Missouri.
It hasn't been this cold for almost two decades in many parts of the country. Frostbite and hypothermia can set in quickly.
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. (AP)