Areas of Montana and the Dakotas were forecast to reach lows in the minus-20s, while parts of California could see the thermometer drop to the 20s. The icy arctic blast was expected to be followed by another one later in the week, creating an extended period of cold weather that hasn't been seen since the late 1990s, meteorologists said.
The unrelenting storm has spread about 2 feet of snow in northeastern Minnesota. The heavy snow and ice has contributed to hundreds of traffic accidents around Minnesota and was cited in at least four fatal crashes since Monday. The snow storm closed the University of Minnesota Duluth and most other schools in the area.
In Colorado, the American Red Cross opened a warming shelter in a church in Black Forest near Colorado Springs, to help people still recovering from a wildfire in June that destroyed nearly 500 homes and killed two people.
Officials warned residents to protect themselves against frostbite if they are going to be outside for any length of time.
"When it gets this cold, you don't need 30, 40 mile-per-hour winds to get that wind chill down to dangerous levels. All it takes is a little breeze," Kines said.
The storm hit the northern Rockies on Monday and Tuesday, dumping up to 2 feet of snow in the mountains and in Yellowstone National Park.
A four-vehicle crash in central Montana killed Chelsea Stanfield, 21, of Great Falls. Authorities said Stanfield was driving too quickly for the icy conditions.
In North Dakota, Ronald Waters, 59, of Watford City, died when the semitrailer he was driving rolled in a ditch south of the city.
In the Dakotas, cattle ranchers who lost thousands of animals in an October blizzard were bracing for the latest wintry weather, with wind chills of 40 degrees below zero expected by week's end.
Cattle should be able to withstand the harsh conditions better than they did the Oct. 4 blizzard, said Julie Ellingson, executive vice president of the North Dakota Stockmen's Association.
"Cattle are a hardy species; they can endure a lot," she said. "With that October storm, they didn't have their winter hair coat yet. They've acquired some of that extra hair that will help insulate them better."
The cold was expected to keep pushing south and bring near-record low temperatures to parts of California. Citrus famers in the Central Valley checked wind machines and ran water through their fields in anticipation of temperatures at or below freezing Tuesday night, followed by even colder weather on Saturday.
However, farmers should not panic, said Bob Blakely of California Citrus Mutual, a trade association. Cold weather can be good for the crops, he said.
"Trees and fruits need some of that cold weather to harden off and prepare for late December and January," he said.
The system was pushing south, and Texans enjoying balmy 80-degree days should be seeing temperatures in the 40s by Thursday, Kines said.
The cold air is expected to linger until next week then move east, where it will bring less-drastic temperature changes, he said.
AP writers Ben Neary in Cheyenne, Wyo., Blake Nicholson in Bismarck, N.D., and Scott Sonner in Reno, Nev., contributed to this report.