(Reuters) - As the Midwestern United States shivered through the region's lowest temperatures in two decades and forecasters warned that life-threatening cold was heading eastward, officials in Chicago and other districts said schools would be closed on Monday.
Icy conditions snarled travel across the Midwest and thousands of flights were canceled or delayed, days after the Northeast was hammered by the first winter storm of the season.
"The coldest temperatures in almost two decades will spread into the northern and central U.S. today behind an arctic cold front," the National Weather Service said on Sunday. "Combined with gusty winds, these temperatures will result in life-threatening wind chill values as low as 60 degrees below zero (Fahrenheit/minus 51 degrees Celsius)."
In weather that cold, frostbite can set in on uncovered skin in a matter of minutes, experts warned.
Minnesota Governor Mark Dayton ordered all public schools in the state closed on Monday to protect children from dangerously cold weather.
Chicago public schools followed suit - reversing an earlier decision - saying in a statement on its website that it would be dangerous for children to commute to school amid sub-zero temperatures and high winds.
The NWS said the widespread chill was a result of a relatively infrequent alignment of weather conditions, allowing the Arctic polar vortex to be displaced unusually far south.
"The weather pattern across North America right now is set up to be very favorable for the southward transport of Arctic air," said Bob Oravec, a National Weather Service meteorologist.
"It's not going to be long-lived," he added. "By the end of the week the temperatures definitely start to moderate across the whole of the country."
COLDEST GAME IN NFL HISTORY?
National Football League fans braved the Wisconsin weather to see the San Francisco 49ers beat the Green Bay Packers 23-20 on a last-second field goal by kicker Phil Dawson.
Jacquie Tucker Braun, 44, was undaunted by a forecast for temperatures below zero F (-17.8 C).
"It's going to be a challenge to stay warm, but we're up to it," said Braun, who plans to bring her 14-year-old son Gryphon to the game. She is bundling up for the game, wearing four layers on top and three layers on the bottom, along with two pairs of socks and two pairs of gloves. "Being a Packers fan is in your blood, hereditary even."
Officials at the Packers' Lambeau Field had promised fans two free hot cocoa or coffee drinks, sports network ESPN reported.
Elsewhere in the Midwest, forecasters warned Chicago and Indianapolis could see overnight lows of minus 12 F (-24 C), Minneapolis minus 29 F (-34 C) and Fargo, North Dakota, minus 31 F (-31 C). The coldest temperature reported in the lower 48 states on Sunday was minus 40 F (-40 C) in the towns of Babbitt and Embarrass, Minnesota, according to the National Weather Service.
In Minnesota, hundreds of residents were evacuated from an apartment building in Rogers on Sunday morning when a backup propane heating system in use because of the extreme cold exploded, police said.
The force of the blast knocked some residents out of bed and others off their feet but caused no serious injuries, said Rogers Police Chief Jeff Beahen.
The temperature was about minus 10 degrees Fahrenheit (-23 C) when the explosion occurred at 8:40 a.m. local time, Beahen said. The blast was followed by additional explosions that continued for half an hour until a fuel valve was turned off, he added.
The cause of the incident is under investigation, Beahen said, and most residents have been allowed back into their homes.
Between 6 inches and a foot of snow was predicted from Chicago to Detroit, AccuWeather said, while icy sleet and rain was forecast for much of the Northeast, where a brief thaw was forecast before intense cold returned late Monday.
More than 7,300 flights were delayed and 3,514 were canceled in the United States on Sunday, according to Flightaware.com, a website that tracks air travel.
Half of the flights in and out of Chicago's O'Hare International Airport were delayed on Sunday, Flightaware reported, as the city was pummeled by a storm that dropped a foot of snow in some places.
In New York City, John F. Kennedy International Airport was closed for a couple of hours on Sunday morning after a Bombardier jet skidded off a taxiway soon after landing.
GLOVES, FIREWOOD AND CHIPS
The cold snap, which comes during the slowest time of the year for shopping, could benefit retailers as they get ready to replace winter merchandise on shelves with spring items in a few weeks.
"It's mostly going to be dry, bitter cold so any retailer that has inventory left over from the holidays - jackets, scarves, hats, gloves - they need to clear that," said Evan Gold, senior vice president at Planalytics, a weather consulting firm in Berwyn, Pennsylvania.
In Nashville, Tennessee, where temperatures were forecast to drop from about 56 F (13 C) in the afternoon to 8 F (-13 C)overnight, Bradley Hite's firewood sales company FirewoodNashville.com was struggling to keep up with demand.
"It's been a lot more business (in the last couple of days). Just a lot more people coming in and picking it up. It's not normal," he said.
In Clintonville, Ohio, Janine Dunmyre found her local grocery store stripped of staples including milk, eggs and juice - as well as some less-essential supplies.
"The chips aisle was decimated," she said. "Like everyone is planning to sit around for two days with snack food."
Dunmyre said she has already made plans for her four children to stay home from school on Monday due to cold temperatures and ice on the roads.
"I'm concerned more about everything turning to ice, not how much snow we are or aren't suppose to get," she said. "Wet power lines iced over means no power."
(Additional reporting by Phil Wahba and Jonathan Kaminsky in New York, Karen Pierog in Chicago and Tim Ghianni in Nashville; Writing by Jonathan Allen; Editing by Edith Honan and Eric Walsh)