An enormous, brutal mass of arctic air is shoving south over most of the United States—threatening 32 million people for the rest of the week with snow, ice, wind and extraordinary drops in the temperature.
Some of the country's biggest cities are being hit: Ice threatens to knock out power in Dallas, Denver could get almost a foot of snow, and Chicago could plunge from the mid-50s on Wednesday to the low teens by Friday night.
"This cold air is going to overtake just about the entire country," said Carl Parker, a meteorologist for The Weather Channel.
In Duluth, Minn., more than 2 feet of snow fell Tuesday, and at least another foot is expected Wednesday. Many streets are already impassable, and police reported dozens of crashes on snowy roads. By Friday, the temperature there could be minus 22.
More from NBC News:
The heavy snow in Minnesota is expected to be compounded by wind as strong as 40 mph. Because the snow is relatively light in weight, not the soggy, clumpy variety, it could cause "ground blizzard" conditions there, Parker said.
The weather system is also expected to bring heavy snow to the Rockies and ice to the Plains. But it is most notable for its incredible reach. Only the coastal states of the East are expected to be spared.
In Pullman, Wash., the temperature fell below zero on Wednesday for the first time in almost three years. In Oregon, authorities closed part of Interstate 84 on Tuesday as trucks jackknifed in the snow.
In California, temperatures Wednesday fell into the 30s in typically mild San Francisco. In the Central Valley, where 85 percent of the citrus crop is still on the vine, growers are worried about devastating damage.
The National Weather Service issued a winter storm warning for parts of Oklahoma and Arkansas for Thursday. In Lubbock, Texas, the high on Tuesday was 77. The low Saturday morning could be below 10.
The weather service reported 6 inches of snow at Jacob Lake, Ariz., and the temperature at Ely, Nev., reached minus 17 early Wednesday morning, and the wind chill overnight hovered at about minus 30.
Provo, Utah, more used to snow this time of year, got 8 and a half inches on Tuesday, and the airport at Salt Lake City got 5.8 inches, shattering the previous record for the date by more than 2 inches.
Texas and the Mid-South—as far south as Dallas and all the way up to Paducah, Ky., faced what Kevin Noth, a lead meteorologist for The Weather Channel, called "the big ice threat," as much as an inch.
"We measure ice in thickness," he said, "and generally speaking, a half-inch is significant because it weighs down the trees and the power lines, causing power outages."
The ice threat for the second half of the week will come as the arctic air mass combines with moisture streaming north from the Gulf of Mexico.
In the Dakotas, the extreme cold posed a threat to cattle ranchers, who lost thousands of their stock in a blizzard in early October. The good news is that cattle have grown some of their winter hair by now, providing insulation.
"Cattle are a hardy species," Julie Ellingson, executive vice president of the North Dakota Stockmen's Association, told The Associated Press. "They can endure a lot."
—By Daniel Arkin, Henry Austin and Erin McClam of NBC News