A frigid weather system called the polar vortex gripped much of the Midwest on Monday as temperatures dropped to near-record, subzero lows, canceling school classes, grounding thousands of airline flights and prompting authorities to urge residents to stay home or go to emergency warming shelters.

In Chicago, temperatures dropped to a record 16 degrees below zero at O'Hare International Airport on Monday, spawning a new National Weather Service Twitter hashtag: "#Chiberia.” In Minneapolis, it was minus 18 -- minus 40 with wind chill. Across the region, forecasters said freezing winds Monday could force temperatures into the minus 60s.

“The big story was the wind chill factors,” said Jim Keeney, a meteorologist at the National Weather Center’s regional headquarters in Kansas City, Mo., adding that the subzero temperatures were “something we haven’t seen in 10 to 15 years.”

As one result, about 3,300 flights were canceled nationwide Monday, and more than 2,000 were delayed, according to flightaware.com.

In Kansas City, the overnight low Sunday was 25 below with wind chill, Keeney said, just shy of the record: minus 13 degrees, set in 1912.

Mike O’Connell, a spokesman for the Missouri State Emergency Management Agency, said officials were prepared for the deep freeze.

“The good news is that this wasn’t an ice storm, so we don’t have massive power outages,” O’Connell said, “The people of Missouri did a really good job of staying off the roads and allowing road crews to do their jobs.”

He said officials also attempted to aid those who might not have a place to shelter from the cold.

“The city of St. Louis made an especially strong effort to take care of homeless people and bolstering their shelters,” O’Connell said.

In Indianapolis, where the temperature dropped Monday to 14 below -- minus 40 with wind chill -- Mayor Gregory Ballard, calling the weather “unprecedented,” issued a warning that barred all but emergency travel until at least noon. The last time city officials issued such a travel warning was during a blizzard in 1978.

In addition to frigid temperatures, the city was also hit Sunday with about a foot of snow, which downed trees and power lines and left about 30,000 people without power, according to Marc Lotter, a spokesman for the mayor’s office.

He said Indianapolis police and social services staff went out last week to warn the city’s homeless to take shelter ahead of the storm, and that officials opened additional shelters.

Many heeded that advice, Lotter said, but because of added power outages Monday, “we’re working to evacuate people to shelters and warming centers.”

“Really, it’s the severe cold that’s the real threat. It can cause frostbite in a matter of minutes,” he said, noting that temperatures in the area are not expected to climb above zero until Wednesday.

Keeney, the meteorologist, said the cold high-pressure weather system responsible for the freezing weather is expected to hover for the next 24 to 36 hours. After that, he said, frigid temperatures are expected to continue in North Dakota, northern Minnesota, Michigan and central Wisconsin, but moderate elsewhere.

The cold will gradually shift east, but “nothing like what we’re seeing across the Midwest and Ohio Valley today,” he said.

By Tuesday, East Coast temperatures are expected to drop dramatically -- to the teens in Boston, New York and Philadelphia. Tuesday's forecast high in New York is 14 degrees, compared with Monday's 55 degrees.

New York had wind chill advisories in effect, with the deep cold expected to move through the area late Monday, delivering what Keeney called “a quick shot of extremely cold weather" that could drive temperature down to a possible low, with wind chill, of 10 below zero.

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