HELENA, Mont. (AP) — An icy blast of arctic air sent temperatures plunging as much as 40 degrees below normal Tuesday across the western half of the nation soon after a storm snarled roadways in the Rockies and threatened citrus crops in California.
The cold snap was expected to spread as far south as Texas by the weekend before turning east, AccuWeather meteorologist Tom Kines said.
"It's a pretty impressive air mass that's coming down out of Canada," he said. "Everybody affected will see temperatures 20, 30 degrees below normal. Some areas will be 40 below normal."
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.
Temperatures were expected to fall below zero with wind chills dropping below minus 20 degrees, said National Weather Service meteorologist Dave Bernhardt in Great Falls, Mont. Such cold weather over a prolonged period of time has not been seen in Montana since the late 1990s, he said.
"The duration is probably what caught most people's eye," Bernhardt said. "It looks like this could last a week."
The weather has created frostbite dangers for anybody staying outside for any length of time, and officials warned residents to take precautions.
Snow and ice created hazardous driving conditions throughout the West, and were a factor in a four-vehicle crash in central Montana that killed 21-year-old Chelsea Stanfield of Great Falls. Authorities said Stanfield was driving too fast for the conditions.
The weather also closed a stretch of Interstate 90 on Tuesday between Sheridan and Buffalo, Wyo. In eastern Oregon, authorities closed much of Interstate 84 as trucks jackknifed in the snow. In Utah, transportation authorities reported dozens of crashes.
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 jet stream is much farther south than normal, allowing the cold air to push in from the Arctic, Kines said. Areas such as Palm Springs, Calif., which typically has high temperatures in the low 70s at this time of year, could see highs in the 50s and lows in the 20s.
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., and Blake Nicholson in Bismarck, N.D., contributed to this report.