Nick warms himself on a steam grate with three other homeless men by the Federal Trade Commission, just blocks from the Capitol, during frigid temperatures in Washington, Saturday, Jan. 4, 2014. A winter storm that swept across the Midwest this week blew through the Northeast on Friday, leaving bone-chilling cold in its wake. (AP Photo/Jacquelyn Martin)

SIOUX FALLS, S.D. - It has been decades since parts of the U.S. Midwest experienced a deep freeze like the one expected to arrive Sunday, with potential record-low temperatures heightening fears of frostbite and hypothermia — even in a region where bundling up is second nature.

This "polar vortex," as one meteorologist calls it, is caused by a counterclockwise-rotating pool of cold, dense air. The frigid air, piled up at the North Pole, will be pushed down to the U.S., funneling it as far south as the Gulf Coast.

Ryan Maue, of Tallahassee, Florida, a meteorologist for Weather Bell, said records will likely be broken during the short yet forceful deep freeze — a perfect combination of the jet stream, cold surface temperatures and the polar vortex — that will begin Sunday and extend into early next week.

"All the ingredients are there for a near-record or historic cold outbreak," he said "If you're under 40 (years old), you've not seen this stuff before."

Before the polar plunge, Saturday marked the day Earth is the closest it gets to the sun each year. The planet orbits the sun in an oval and on average is about 93 million miles (149.7 million kilometres) away. But every January, Earth is at perihelion, and on Saturday, it was only 91.4 million miles (147.1 million kilometres) from the sun.

But that proximity doesn't affect the planet's temperatures, and the predictions are startling: 25 below zero Fahrenheit (31 below zero Celsius) in Fargo, North Dakota, minus 31 F (minus 35 C) in International Falls, Minnesota, and 15 below F (26 below C) in Indianapolis and Chicago. At those temperatures, exposed skin can get frostbitten in minutes and hypothermia can quickly set in as wind chills may reach 50, 60 or even 70 below zero F (45.5, 51 or even 56.7 below zero C).

Even wind chills of 25 below zero F (31.5 below zero C) can do serious damage, according to National Weather Service meteorologist Scott Truett in St. Louis.

"Those are dangerous levels of wind chill," he said of the expected wind chill in Missouri at daybreak Monday. "A person not properly dressed could die easily in those conditions."

The cold will sweep through parts of the northeastern New England states, too, where residents will have just dug out from a snowstorm. And fresh powder is expected in parts of the central Midwest and South starting Saturday night — up to a foot (30 centimetres) in the St. Louis area, 6 to 8 inches (15 to 20 centimetres) in central Illinois, 8 or more inches (15 or more centimetres) in western Kentucky and a half-foot to a foot (15 to 30 centimetres) in southwestern Michigan.

Snow will reduce the sun's heating effect, so nighttime lows will plummet because of strong northwest winds that will deliver the Arctic blast, Maue said. There's no warming effect from the Gulf to counteract the cold air, he said.

Even places accustomed to mild and warmer winters will be affected early next week, including Atlanta where Tuesday's high is expected to hover in the mid-20s F (around minus 4 C).

Sunday's National Football League playoff game in Green Bay, Wisconsin, could be among one of the coldest ever played — a frigid minus 2 degrees F (minus 19 degrees C) when the Packers and San Francisco 49ers kickoff at Lambeau Field. And ice skaters in Des Moines, Iowa, won't be able to use an outdoor rink, as officials decided to shut it down Sunday and Monday.

States are trying to get ahead of the storm, with Minnesota calling off school Monday for the entire state — the first such closing in 17 years.

Although this cold spell will last just a few days, it likely will freeze over the Great Lakes and other bodies of water, meaning frigid temperatures probably won't go away for the rest of the winter, Maue said. He also noted that it's relatively uncommon to have such frigid air blanket so much of the U.S., maybe once a decade or every couple of decades.

In the U.S. Northeast, forecasters said temperatures will rise over the weekend before plunging again.

At least 16 deaths were blamed on the storm as it swept across the eastern half of the U.S., including three people who officials said died at least partly because of the extreme cold.

The snowfall had all but stopped by Friday morning in the hard-hit Philadelphia-to-Boston corridor and though the temperatures reached only the teens or single digits F (up to about minus 7 C) , the cold kept the snow powdery and light.

The heaviest snow fell north of Boston in Boxford, Massachusetts, which received nearly 2 feet (60 centimetres). Nearly 18 inches (45 centimetres) fell in Boston and in western New York near Rochester. New York's Central Park got 6 inches (15 centimetres), and Philadelphia got more than 6 inches (15 centimetres).

Temperatures reached 8 below zero F (22 below zero C) in Burlington, Vermont, with a wind chill of 29 below F (34 below C), and 2 degrees F (minus 17 C) in Boston.

Warming centres opened around the region, homeless shelters received more people, and cities took special measures to look after those most vulnerable to the cold. Teams in New York City searched the streets for homeless people.

The light, powdery snow was a blessing in another respect: It did not weigh down electrical lines or tree limbs, and as a result there were only a few thousand power outages across the Northeast.

Slick roads were blamed for several traffic deaths. In addition, a 71-year-old woman with Alzheimer's disease froze to death after she wandered away from her rural western New York home. A Wisconsin man died of hypothermia outside his home in Milwaukee, where the temperature dropped below zero F (below minus 18 C) early Friday. And a worker in Philadelphia was killed when a 100-foot (30-meter)-high pile of road salt fell and crushed him.

Schools as far south as Washington, D.C., were closed on Friday. Many government offices also shut down.

Airports across the region struggled to resume normal operations after U.S. airlines cancelled around 2,200 flights Friday, on top of 2,300 the day before.

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Associated Press Writer Seth Borenstein in Washington and Bill Draper in Kansas City, Missouri, contributed to this report.

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Online:

Maps: http://1.usa.gov/19FjxxS

Wind chill: http://1.usa.gov/19FjvpT

Records: http://1.usa.gov/19Fjy59

News from © The Associated Press, 2014