CHICAGO — A year after a brutal cold spell was blamed on something called the polar vortex — which was treated like a northern invasion by the media and as a conquering hero by children impressed by its power to close schools — this week's chill is little more than what meteorologists like to call winter.
Here are some questions — and answers — about the weather:
Q: WHAT'S THE FORECAST?
A: The Midwest will see the tail end of a storm that could dump as much as 6 inches of snow on Chicago by early Tuesday. That city, which awoke to sub-zero temperatures Monday, is expected to warm to a high of 16 degrees Tuesday before temperatures plummet to as low as 10 degrees below zero Wednesday morning and no higher than 5 degrees the rest of the day.
The temperatures pale in comparison to those experienced in North Dakota and Minnesota, where wind chills of between negative 25 and negative 50 degrees hit Monday morning.
Rainy New York City will also be struck by the cold come Thursday and "will be lucky if it hits 20" with lows near 10 degrees, according to Michael Musher with the National Weather Service's Weather Prediction Center.
It will be unusually cold in Atlanta on Thursday, when temperatures are forecast to dip into the lower teens, before scrambling up to the lower 20s on Friday.
In the West, a stream of Pacific moisture that dropped as much as 7 inches of rain along the Washington coast is expected to give way to clear skies. Flooding washed out foundations of a few houses and forced the evacuation of about 60 nursing home residents in Hoquiam in western Washington. Some rivers are already flooding or are expected to reach flood stage by Tuesday.
Q: WHAT'S CAUSING THE TEMPERATURE DROP?
A: The jet stream is dipping, meaning cold air from Canada and other northern areas is plummeting into the eastern two-thirds of the United States.
Q: IS IT THE POLAR VORTEX?
A: The phrase took on a life of its own last year, becoming wildly popular on television news and in social media, and serving as fodder for late night comedians, not to mention Rush Limbaugh, who suggested it was an invention of liberals making their case in the debate over global warming.
"We've been told to go around that term," said Musher, chuckling.
The answer is yes and no. Yes, because as Musher noted, the cold air is coming from near the North Pole. But no, because the system itself that came all the way down into the United States has so far stayed in its normal location far to the north of the U.S. border.
Meteorologists say it's simply winter.
Q: HOW CAN PEOPLE PREPARE?
A: Officials in the coldest areas urged residents to bundle up to guard against hypothermia and exercise caution while driving.
In the North Dakota city of Belcourt, the temperature was recorded at minus-48, with the wind chill. That degree of cold can cause frostbite to exposed skin within a matter of minutes, but "up here, where we're at, we're used to it," said Jake McCloud, assistant manager of the Utter Stop convenience store in Belcourt. "We don't get too many (customers) who complain."
In Montana, snow and freezing rain triggered highway accidents, school closures and avalanche warnings. One to 2 feet of snow had fallen by Monday morning in the Whitefish and Kalispell areas.
"We're definitely concerned for travelers out there, people on the roadways when conditions are fine one moment, then visibility drops," said Paul Nutter with the National Weather Service in Great Falls, Montana.
Q: WHAT'S NEXT?
A: Temperatures are expected to be lower than normal for days but could rise a bit by the end of the week.
"We have cold temperatures, but it's not like it never happened before," said Bob Oravec, a meteorologist with the Weather Prediction Center in College Park, Maryland. "It's typical for an Arctic outbreak."
Associated Press writers Blake Nicholson in Bismarck, N.D., and Matthew Brown in Billings, Mont., contributed to this report.