SIOUX FALLS, S.D. » The deep freeze expected to arrive Sunday in parts of the United States will be one to remember, with potential record-low temperatures heightening fears of frostbite and hypothermia.

It hasn’t been this cold for decades — 20 years in Washington, D.C., 18 years in Milwaukee, 15 in Missouri — even in the Midwest, where bundling up is second nature. Weather Bell meteorologist Ryan Maue said, "If you’re under 40 (years old), you’ve not seen this stuff before."

Blame it on a "polar vortex," as one meteorologist calls it, a counterclockwise-rotating pool of cold, dense air.

"It’s just a large area of very cold air that comes down, forms over the North Pole or polar regions … usually stays in Canada, but this time it’s going to come all the way into the eastern United States," said National Weather Service meteorologist Phillip Schumacher in Sioux Falls, S.D.

The frigid air — a perfect combination of the jet stream, cold surface temperatures and the polar vortex — will begin Sunday and extend into early next week, funneled as far south as the Gulf Coast.

The predictions are startling: 25 below zero in Fargo, N.D., minus 31 in International Falls, Minn., and 15 below 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.

Even wind chills of 25 below zero 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."

Already, parts of New England dropped into the negatives early today, with East Brighton, Vt., seeing 30 below zero just after midnight and Allagash, Maine, hitting minus 36. The cold will sweep through other parts of New England where residents are digging out from a snowstorm.

Snow will reduce the sun’s heating effect, so nighttime lows will plummet because of the strong northwest winds, Maue said. Fresh powder is expected in parts of the central Midwest and South starting tonight — up to a foot in eastern Missouri and southern Michigan, 6 to 8 inches in central Illinois, 8 or more inches in western Kentucky and up to 6 inches in parts of middle Tennessee.

The South also will dip into temperatures rarely seen. By Monday morning, western and central Kentucky could be below zero — "definitely record-breaking," said weather service meteorologist Christine Wielgos in Paducah, Ky. And in Atlanta, Tuesday’s high is expected to hover in the mid-20s.

Sunday’s NFL playoff game in Green Bay could be among one of the coldest ever played — a frigid minus 2 degrees when the Packers and San Francisco 49ers kickoff at Lambeau Field. Medical experts suggest fans wear at least three layers and drink warm fluids — not alcohol.

Minnesota has called off school Monday for the entire state — the first such closing in 17 years — as well as the Wisconsin cities of Milwaukee and Madison.

Before the polar plunge, Earth was as close as it gets to the sun each year today. The planet orbits the sun in an oval and on average is about 93 million miles away. But every January, Earth is at perihelion, and today, it was only 91.4 million miles from the sun. But that proximity doesn’t affect the planet’s temperatures.

Maue 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. Yet, Truett said there are no clear trends in weather patterns to indicate what kind of temperatures are in store for the rest of the winter.

So far, this winter is proving to be a cold one.

"Right now for the winter, we will have had two significant shots of major Arctic air and we’re only through the first week of January," Maue said.

Online:

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

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

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

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Associated Press reporters Seth Borenstein and Shelley Adler in Washington; Bill Draper in Kansas City, Mo.; and Rebecca Yonker in Louisville, Ky., contributed to this report.