A blast of swirling, bitterly cold dense air known as a "polar vortex" settled Monday across large parts of the USA as the nation braced for what could be record low temperatures.
The forecast is extreme: 32 below zero in Fargo, N.D.; minus 21 in Madison, Wis.; and 15 below zero in Minneapolis, Indianapolis and Chicago. Wind chills — what it feels like outside when high winds are factored into the temperature — could drop into the minus 50s and 60s.
"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 at 15 to 30 below zero.
Indianapolis Mayor Greg Ballard 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 during the 1978 blizzard.
For several Midwestern states, the bitter cold was adding to problems caused by a weekend snow storm. The National Weather Service said the snowfall at Chicago's O'Hare International Airport totaled more than 11 inches as of 6 p.m. Sunday — the most since the Feb. 2, 2011, storm that shut down the city's famed Lake Shore Drive.
Missouri transportation officials said it was too cold for rock salt to be very effective, and several Illinois roadways were closed because of drifting snow.
A bus taking the Southern Illinois University men's basketball team home from a game at Illinois State got stuck in the snow Sunday night off Interstate 57, forcing the group to wait for a tow truck and make plans for a night at a hotel in nearby Tuscola, Ill.
On Sunday, more than 4,000 flights had been canceled, creating more havoc for air travel. Another 10,000 flights were delayed, according to FlightStats.com. By early Monday, over 2,000 more flights had already been called off, with hundreds more delayed.
"There is nothing routine about a weather event such as this," says Jim Hetzel, a vice president of FlightStats, based in Portland, Ore.
Many cities came to a virtual standstill. In St. Louis, where more than 10 inches of snow fell, the Gateway Arch, St. Louis Art Museum and St. Louis Zoo were part of the seemingly endless list of things closed. Shopping malls and movie theaters closed, too. Even Hidden Valley Ski Resort, the region's only ski area, shut down.
School was called off Monday for the entire state of Minnesota, as well as cities and districts in Wisconsin, Illinois and Indiana and Iowa, among others. Chicago Public School officials reversed an earlier decision to keep schools open, announcing late in the day Sunday that classes would be canceled Monday.
Government offices and courts in several states closed Monday. In Indiana, the General Assembly postponed the opening day of its 2014 session, and the state appellate courts, including the Indiana Supreme Court, said they would be closed.
New York City and parts of the East were still wrestling with an earlier front that dumped a mix of snow, freezing rain and rain across much of the region. At John F. Kennedy International Airport, a plane slid into snow Sunday morning, prompting the airport to suspend operations for about two hours because of icy runways.
Southern states are bracing for possible record temperatures, too, with single-digit highs expected Tuesday in Georgia and Alabama.
Temperatures are expected to dip into the 30s in parts of Florida on Tuesday. Though Florida Citrus Mutual spokesman Andrew Meadows said it must be at 28 degrees or lower four hours straight for fruit to freeze badly, fruits and vegetables were a concern in other parts of the South.
With two freezing nights ahead, Louisiana citrus farmers could lose any fruit they cannot pick in time.
In Plaquemines Parish, south of New Orleans, Ben Becnel Jr. estimated that Ben & Ben Becnel Inc. had about 5,000 bushels of fruit on the trees, mostly navel oranges and the sweet, thin-skinned mandarin oranges called satsumas.
"We're scrambling right now," he said.
Contributing: USA TODAY's Kim Hjelmgaard in London; Indianapolis Star; Associated Press