(CNN) -- A blast of Arctic air Tuesday morning has much of the nation -- from the Great Lakes to Oregon and down to Texas -- in its cold, icy grip.



Snow covers a golf course in Summerlin, Nevada, near Las Vegas, on Monday.



The temperature at International Falls, Minnesota, was 26 below zero at 8 a.m. Tuesday, the National Weather Service said.



To the south in Minneapolis, below-zero temperatures were leaving roadways covered in black ice, sending drivers spinning into numerous accidents, CNN affiliate KARE-TV reported Tuesday.



Black ice, nearly invisible on roads, can form when car exhaust freezes on snow-covered pavement in sub-zero conditions, KARE said. Twin Cities drivers could find a little hope in the day's forecast high -- 4 degrees above zero by the afternoon.



Temperatures hovering as low as 23 below zero have parts of Montana frozen in their tracks, according to CNN affiliate KFBB-TV.



The forecast high Tuesday for Great Falls: 5 degrees.



But regions of the nation far from Montana, and not as well equipped to deal with wintry weather, are also caught in the cold blast.  Watch the mess in Portland, Oregon »



WFAA-TV in Dallas, Texas, predicts the temperature will barely get above freezing, to 36 degrees, on Tuesday. A winter weather advisory is in effect for northern Texas.



In Las Vegas, Nevada, residents saw a rare snow accumulation.



Snow-covered grounds were a treat for iReporter Rena Moretti, who's lived in Las Vegas on and off for about 10 years.



"It's unbelievable. If it snows it never sticks. I've never seen it like that," she said.   Watch snow delight skiers but frustrate motorists in Nevada »  In Denver, Colorado, where the temperature was minus 4, KMGH warned residents to expect more snow, with 2 to 3 feet expected in some parts of the Rocky Mountains.  Watch ice cause havoc on Colorado roads »



While the snow is forecast to end Tuesday, the cold air mass should stick around all week. The station also warned commuters that driving would be a mess Tuesday morning.



In Omaha, Nebraska, the frigid weather had shelters sending out crews looking for the homeless, according to KMTV.  Watch blizzards shut down North Dakota »



"We've had people that have been trying to make it here ... either have been too intoxicated or just too cold and just fallen down and haven't been able to make it," says Siena Francis House worker and guest Jerry Rayburn.



According to the National Weather Service, the entire state of Iowa could be in for heavy snowfall Tuesday. Chicago, Illinois, no stranger to cold weather, is expecting a high of 22 degrees with snow, according to WGN.



Meanwhile, on a frontal boundary, West Virginia and western Tennessee are on the alert for possible freezing rain, the weather service reports. And KATV in Little Rock, Arkansas, said freezing rain and sleet were moving across the state.



In New England, socked by a powerful ice storm last week, temperatures were warming back up into in the 40s and 50s, WCVB in Boston, Massachusetts, reported.



But electricity may not be restored to some customers until the weekend, the station reported.



One town, Lunenberg, Massachusetts, said school students would be getting an extended Christmas break, with classes not resuming until the new year, WCVB reported. Debris-clogged roads were blamed.



"They're passable for vehicles and emergency vehicles, but they're not passable for buses. That represents a danger, so, we can't get the kids safely to school, even if we were able to open school," School Superintendent Loxi Joe Calmes said, accoding to WCVB.



Meanwhile, a cold, wet storm blew into Southern California. Twenty-four-hour rainfall totals were 1.44 inches at Los Angeles International Airport, almost 1 inch in Palm Springs, and an inch in San Diego, the weather service reported Tuesday morning. iReporters share their
What is affecting a large swath of the US? Which areas are in a wintry grip? What caused the city to close schools? What is plaguing Minneapolis? Where is the black ice located? What color are the Ice plagues? What has happened to the schools?
blast of Arctic air and down to Texas Debris-clogged roads black ice, Minneapolis, black classes not resuming until the new year,
question: What is affecting a large swath of the US?, answer: blast of Arctic air | question: Which areas are in a wintry grip?, answer: and down to Texas | question: What caused the city to close schools?, answer: Debris-clogged roads | question: What is plaguing Minneapolis?, answer: black ice, | question: Where is the black ice located?, answer: Minneapolis, | question: What color are the Ice plagues?, answer: black | question: What has happened to the schools?, answer: classes not resuming until the new year,