Snow and ice blanket downtown St. Louis and the Mississippi River on Wednesday, January 8.
People wait outside the Broadway Theatre in New York City to buy tickets for the show "Cinderella" on January 8.
Water dripping from a New York City subway station freezes on a traffic cone January 8.
A man walks past a car in Baltimore that is partially covered in ice January 8.
Ice collects on the Delaware River near Philadelphia on January 8.
Icicles hang from the bumper of a vehicle in Fort Walton Beach, Florida, on Tuesday, January 7.
A vehicle drives through a barely visible intersection in Stafford, New York, on January 7.
Plants covered in ice are seen in Panama City Beach, Florida, on January 7.
Ice in the Mississippi River flows past the Gateway Arch in St. Louis on January 7.
Ice forms around rocks on the Brooklyn waterfront, across from Lower Manhattan, on January 7, in New York City.
A woman braves the cold in Scranton, Pennsylvania, on January 7.
Passengers wait for a train to arrive in Chicago on January 7, when temperatures were below zero.
A man clenches his fists while walking past a steam vent in New York City on January 7.
A man bundles up against the cold in New York City on January 7.
A couple walks past an advertisement in Pittsburgh during sub-zero temperatures January 7.
A woman tries to stay warm while waiting for a bus in Brooklyn, New York, on January 7.
Ice builds up along Lake Michigan at Chicago's North Avenue Beach on Monday, January 6.
With temperatures nearing 0 degrees, a cloud of steam from a manhole blows across an intersection in downtown Pittsburgh on January 6.
Men battle the bitter wind as they walk in Chicago on January 6.
Postal worker Jamie Jasmon struggles to deliver mail in the snow January 6 in Springfield, Illinois.
Vehicles drive down a snow-covered road in Burton, Michigan, on January 6.
Metra employees in Chicago walk around LaSalle Street Station on January 6.
A man warms his hand while running errands in Flint, Michigan, on January 6.
A commuter walks past warming lamps at a Chicago train station on January 6.
A woman props up her feet on her luggage January 6 after her flight home was canceled at Logan International Airport in Boston.
A woman makes her way through a snow drift in downtown St. Louis on January 6.
A man shovels the snow off his car in Indianapolis on January 6.
A woman walks to the University of Minnesota's St. Paul campus on January 6.
A man clears the sidewalk in front of his home in Carmel, Indiana, on January 6.
A blanket of fog covers Lake Michigan along the Chicago shoreline January 6.
A man braves the snow in downtown Springfield as a winter storm moves across the Midwest on Sunday, January 5.
A car is buried in snow January 5 in Zionsville, Indiana.
A city snowplow clears the street in an almost-deserted downtown Springfield on January 5.
With the Gateway Arch in the distance, a person struggles to cross the street during a snowstorm January 5 in downtown St. Louis.
Snow covers a garden gnome in St. Louis on January 5.
Anna Maksimkina of Yekaterinburg, Russia, sleeps on the floor at John F. Kennedy International Airport in New York after a Delta flight from Toronto to New York skidded off the runway into a snow bank, temporarily halting all flights January 5.
Four homeless men warm themselves on a steam grate by the Federal Trade Commission Building, blocks from the U.S. Capitol in Washington, as frigid temperatures grip the nation's capital on Saturday, January 4.
People go sledding in Prospect Park in Brooklyn, New York, on January 4.
Snow is piled high in front of a Home Depot in Boston on January 4.
Sunlight beams through the windows of a building that caught on fire Friday, January 3, in Plattsmouth, Nebraska. The firefighters' water froze all over the building.
Michael Stanton walks between houses covered with ice in Scituate, Massachusetts, on January 3.
Pedestrians brave wind and snow as they cross New York City's Fifth Avenue on January 3.
Snow clings to the clothing and facial hair of Jerome Williams as he uses a snowblower in front of his home in Roosevelt, New York, on January 3.
Travelers wait in line January 3 at Chicago Midway International Airport.
Frost covers the windows at the Morning Glory natural food store in Brunswick, Maine, on January 3.
Snowplows clear snow from one of the runways at JFK Airport on January 3.
Surfers make their way through snow on New York's Rockaway Beach on January 3.
Passengers wait in line at a security checkpoint at JFK Airport on January 3.
Blowing snow swirls as a worker shovels a platform at a Haddonfield, New Jersey, train station on January 3.
A plane takes off January 3 as trucks plow snow at Newark Liberty International Airport in Newark, New Jersey.
A man walks down a snowy road along the shore in Scituate on January 3.
Postal worker Danny Kim clears snow and ice off the hood of his delivery truck January 3 in Bethesda, Maryland.
A couple walks across a snow-covered parking lot January 3 at Newark Liberty International Airport.
Tourists play in the snow at the base of the Washington Monument on January 3.
People play in Brooklyn's Prospect Park on January 3.
A man walks through the snow as the wind kicks it up January 3 in New York City.
Dante de Blasio, son of New York Mayor Bill de Blasio, shovels snow outside his home in Brooklyn on January 3.
Snow covers subway rails in New York City on January 3.
A man uses his snowblower to clear some paths in Mansfield, Connecticut, on January 3.
Workers clear snow off sidewalks on New York City's Fifth Avenue on January 3.
A man clears snow from a vehicle January 3 in Albany, New York.
A truck-mounted snowblower clears a section of road in Dedham, Massachusetts, on January 3.
A worker clears snow from a subway station in Queens, New York, on January 3. Public schools were closed Friday after up to 7 inches of snow fell in New York City.
A man shovels snow during the tail end of a snowstorm in Brooklyn on January 3.
A man rides an all-terrain vehicle through a Brooklyn street on January 3.
The Kunta Kinte-Alex Haley Memorial is covered in snow in Annapolis, Maryland, on January 3.
A man plows snow January 3 following an overnight snowstorm in Jersey City, New Jersey.
A child sleds down a hill in Chicago's Humboldt Park on Thursday, January 2.
Children make a snow pile in New York's Times Square on January 2.
Winds whip snow from the beach across Winthrop Shore Drive in Winthrop, Massachusetts.
Snow covers bikes along Leavitt Street in Chicago's Wicker Park on January 2.
With his dog in tow, a man skis across heavy snow in Humboldt Park on January 2.
Dallas Todd, 11, flies down a snowy hill at Lake Harbor Park in Norton Shores, Michigan, on January 2.
Snow covers cars in Chicago's Humboldt Park neighborhood on January 2.
A man drags a suitcase on a snowy street in downtown Boston on January 2.
A van is pulled from a ditch along Interstate 94 in Jackson, Michigan, on January 2.
A man walks his dog on the snow-covered Monon Trail in Carmel, Indiana, on January 2.
An airplane waits for passengers at O'Hare International Airport in Chicago on January 2.
A woman walks through snowy conditions in Albany on January 2.
Trucks clear snow off the roads in Torrington, Connecticut, on January 2.
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STORY HIGHLIGHTS
- NEW: Freeze death toll rises to 15, most in traffic accidents
- Too cold for Chicago zoo's polar bear, but not for some Minnesotans
- Polar vortex brings deep freeze from Great Lakes to Deep South
- Extreme wind chills mean exposed flesh can freeze in as little as five minutes
(CNN) -- How cold is it?
It's so cold, even polar bears and penguins were being kept indoors Monday.
Anana, the lone polar bear at the Lincoln Park Zoo in Chicago, has never grown the thick layer of fat that bears in their native Arctic develop to insulate themselves against winter temperatures that can range as low as -50 degrees F, zoo spokeswoman Sharon Dewar said. So when temperatures plunged well into the negative range in Chicago, Anana stayed in a 40ish-degree habitat, Dewar said.
"In the wild, they would seasonally eat seals and fatten themselves up with that blubber," Dewar said. But zookeepers "don't feed them seals or fatten them up," she said.

A Chicago resident's eyelashes froze on the morning of January 6.
CNN iReporter Robert Livesay took this picture of frozen ice bubble he blew in Grove, Oklahoma, on Monday, January 6. "If you have too much wind, the bubbles will blow away," he said.
A little snow won't stop these two from enjoying a run in northeast Ohio on January 6.
A Chicago man heads to work on January 6 with an overcoat and briefcase ... plus a balaclava and ski goggles.
Maranda McClaskey knew the birds in Harrisville, West Virginia, would appreciate extra food in the chilly weather on January 6. But when one poor bird landed on her porch to eat, it got stuck to the ice! Finally the bird managed to free itself -- but it left these feathers behind.
Sixteen-year-old student Christian Arnold photographed a snowdrift in Indiana on January 6. "This is the most dangerous winter weather I have ever witnessed," he said.
In Wisconsin on January 6, temperatures fell to minus 21 degrees, with wind chills below 40.
Nature photographer Candice Trimble bundled up in layers to snap some shots of the frozen conditions outside her home in Front Royal, Virginia, on Sunday, January 5. She watched this water hit the leaf and then completely freeze.
Is this guy nuts?! He's sporting shorts in Chicago on January 6, when the temperature did not rise above 0 degrees Fahrenheit.
Trees are weighed down with snow in the Long Lake area in Michigan on January 5.
The frigid weather inspired photographer Tanya Fuchs to take her camera out around her neighborhood in Fire Island, New York, on Saturday, January 4.
CNN iReporter Joy Lewandowski's son Matt plays in a snow fort built by kids on her street on January 5. School was canceled Monday.
Jason Bentley decided to take a relaxing break in the snow on January 5 in Indianapolis, Indiana, after he learned that his Southwest flight back home to Los Angeles was canceled and rescheduled for Thursday.
CNN iReporter Todd Joyce took this photo of his dog, Ginger, playing in the snow in Ohio on January 5.
Alexandra Leahy ventured outside her apartment complex in Carmel, Indiana, on January 5 to photograph the snowy landscape. "The snow is very white, very glistening, and stuck to everything," she said.
Mark Anthony Baquir captured this photo of a snowy yard in Maryland on Friday, January 3. "It seemed like no one was prepared for the storm in this part of Maryland," he said.
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Reporter: Polar vortex a 'cursed phrase'
Bone-chilling cold to grip much of U.S.
Temperatures plunge in Chicago
Power failures leave Canadians in the dark
And at the National Aviary in Pittsburgh, both bald eagles and African penguins "who are used to temperate climates" were taken off exhibit until the weather warms up, the facility reported.
Chicago saw a record low of minus 16 (minus 27 C) on Monday. The day's high was minus 11, with a windchill of minus 34. It's part of an Arctic blast that plunged deep into the central United States on Monday, leaving Nashville, Tennessee, 40 degrees colder than Albany, New York; Memphis 20 degrees colder than Anchorage, Alaska; and Atlanta colder than Moscow -- Russia or Idaho, take your pick.
The bitter cold that a "polar vortex" is pushing into much of the United States is not just another winter storm. It's the coldest in 20 years in many areas. The South was downright balmy compared to the Great Lakes region, where temperatures hovered in the negative 20s -- before wind chill, which dropped temps to the negative 40s and in places like Minneapolis.
Minnesota Gov. Mark Dayton ordered the state's roughly 2,000 public schools to close on Monday, the first such order since 1997. Many of those will stay closed Tuesday, including the three major districts around Minneapolis, where blowing snow shrouded bridges over the frozen Mississippi River.
"I've only been out of school four days ever, and today and tomorrow are two of the four days," said Graham Myers, who was going to a movie with several friends and his father.
Wind chills in the 40-below range can cause frostbite in a matter of minutes, the National Weather Service warned. But there were those who reveled in it.
"I love the cold. I'm one of those crazy cold-weather Minnesotans who just enjoys this," Robert Pettit told CNN as he took a walk on a work break. If properly dressed, "It's not so bad," he said.
"You dress up, put your mukluks on, get some gloves and a hat and you're set," Pettit said.
Freeze toll 15, mostly from accidents
Authorities have blamed a total of 15 deaths on the cold so far, 11 of them from traffic accidents.
But the the death of an Indianapolis woman found in her backyard early Monday "is believed to be weather-related," police spokesman Kendale Adams told CNN. A man in Wisconsin died of hypothermia, and an elderly woman with Alzheimer's disease who wandered away from her home in New York state was found dead in the snowy woods about 100 yards away, authorities there said.
In addition, hypothermia was a contributing factor in the death of a patient at University Hospitals Case Medical Center in Cleveland, hospital spokesman George Stamatis told CNN.
At the Salvation Army Harbor Light Center, a Minneapolis homeless shelter, Executive Director Bill Miller said 750 people came in off the street to spend the night Sunday.
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"That's a record," he said. He said Harbor Light "will take in everybody, no matter if they've been drinking or whatever their issues might be."
Further south, the chill was less brutal but still nothing to dismiss. In Fairfield, Iowa, at minus 9, CNN iReporter Deborah Roberts called Monday "a good day to stay in and use the excuse it's too darn cold."
In Illinois, Gov. Pat Quinn called on state residents to stay off the roads and activated National Guard troops to help local authorities clear highways. In Chicago, Mayor Rahm Emanuel urged residents "to keep exercising good judgment and remain indoors if at all possible."
8 tips to ease winter travel woes
The deep freeze has also snarled air traffic across the country, with more than 3,800 flights canceled by Monday evening, according to flightaware.com. Among those stuck waiting for a way home was New York resident Mindy Goldberg, whose family's flight back from Mexico had been diverted to Boston because of bad weather.
"I just called my kids' school to tell them they wouldn't be there, and she said, 'Everyone's stuck somewhere,' " Goldberg told CNN affilliate WBZ.
In Indianapolis, Los Angeles resident and iReporter Jason Bentley took some time out to play in the snow outside the airport after learning his flight home had been canceled Sunday. It was 15 below zero.
"This is the wettest snow I've ever touched," Bentley said. "The easiest snow to make a snowman and to have snowball fights. It's also probably the worst (weather) I've ever been in because of the temperature."
The Northeast will be seeing its own swift drop in temperatures as the arctic air works its way east. In New York, where it was about 50 degrees with wind chill Monday morning, could go as low as minus 7 on Tuesday, said CNN meteorologist Indra Petersons -- a nearly 60-degree temperature change in a single day.
Welcome to 'Chiberia'
The National Weather Service adopted the Twitter hashtag "#Chiberia" for Chicago. Parts of the vast Siberian region, such as Tobolsk, had Fahrenheit temps in the low teens Monday, though other parts had temperatures of 50 below zero.
Chicago opened up 12 centers for residents to seek warmth, one of which was to stay open all night through Tuesday. Libraries and some other city facilities would also be open, said Evelyn Diaz of the city's Department of Family and Support Services. Quinn said 100 warming centers were open statewide.
The Southern Illinois University men's basketball team, fresh off a game against Illinois State, got trapped on the side of Interstate 57 late Sunday and was prepared to spend the night on the bus, SIU Athletic Director Mario Moccia said.
There wasn't a massive amount of snow on the ground, Moccia said. Rather, it was the blowing snow that made the road virtually impossible to see. Players later tweeted that they were going to spend the night at a nearby church.
"Somehow this eventful day/night has led to our team sleeping on the floor of a church in Tuscola. What a journey it has been," Dawson Verhines tweeted.
Some of the greatest concern surrounds the tens of thousands of Midwesterners without electricity. More than 15,000 customers in Indiana, 6,800 in Illinois and 2,200 in Missouri didn't have power overnight, according to utility companies.
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The worst was still reaching down South on Monday night. In Atlanta, where Tuesday morning's low was projected to be in the single digits, Katie Fallon joked, "My shoes do not even match my outfit this morning! Had to go fuzzy socks and hiking boots for warmth." Atlanta's public schools were still closed for break Monday, and the city announced schools would remain closed Tuesday.
But by Wednesday, temperatures will start edging closer to normal, and by Thursday temperatures in most of the country will be back to normal -- or even a bit warmer, said CNN meteorologist Brandon Miller.
"It's bitterly 10 degrees here in Weatherford, Texas, with a wind chill of below zero," said Elizabeth Brew. "Very hard to watch my kids go to school in such weather, but it is what it is."
"It's not just a snow event, it's a cold event, and that's what scares us," Indianapolis Mayor Greg Ballard said. He urged residents to stay off the streets, especially after nightfall.
In Embarrass, Minnesota, residents wondered whether they might see their cold-temperature record of 64 below zero, set in 1996, snap like an icicle.
"I've got a thermometer from the weather service that goes to 100 below," resident Roland Fowler told CNN affiliate KQDS. "If it gets that cold, I don't want to be here."
iReport: Watch heavy snow create a beautiful scene in Indiana
CNN's Stephanie Elam, Paul Vercammen, Kevin Conlon, Holly Yan, Dave Alsup, Jareen Imam, David Williams and Dave Hennen contributed to this report.