Many Chicago-area schools will again be closed Tuesday, dozens of the day's flights have been canceled and some area attractions will be shuttered, with the subzero chill maintaining its grip on the region for another day. 
 
 But if there was a silver lining, it could be found both in morning and evening commutes that have been smoother than they were during the deep freeze earlier this month and even in the resolve of Chicagoans to just get through it. 
 
 "I’m a Windy City baby, so I just prepare myself. I'm used to it," said Edna Hackman, 51, who spent the morning with dozens of others doing laundry at a Chatham laundromat despite the cold. "You've got to come out to do what you've got to do. You can't sit up in the house just because it's cold." 
 
 An arctic air blowing across Iowa and southern Minnesota is expected to hold high temperatures Tuesday to 1 degree above to minus 3, with a low of 3 to 10 below zero, according to the National Weather Service. Wind chills could dip as low as 40 below. 
 
 As a result, Chicago Public Schools canceled classes for a second day, as did dozens of private and suburban districts because of the subzero temperatures and wind-chill readings. Public schools in Hinsdale and Elmhurst announced they would close too, and after-school activities there were canceled. 
 
 More than 200 Tuesday flights at O’Hare International and Midway airports were already canceled as of Monday night, according to airline information provided to the flight-tracking service FlightAware. 
 
 That followed a Monday with more than 400 canceled flights, according the Chicago Department of Aviation, and near white-out conditions on some interstates in outlying areas. 
 
 But for most, it was business as usual even as the temperature rapidly dropped to dangerously cold levels. 
 
 “If you live in Chicago, you should know it’s going to get cold,” Hackman said. “And you know it’s going to be here for a while.” 
 
 Only a handful of people were at the Brookfield Zoo on Monday afternoon. Most were parents with small children who sprinted from their cars to the indoor Hamill Family Play Zoo. The indoor zoo has a greenhouse, domestic animals and play areas. 
 
 Oak Park resident Diana Calderon, 33, showed up with her son, Oliver, 2. 
 
 “His play group was canceled for the day so we thought we would come here,” Calderon said. “We are just tired of being in the house. He (Oliver) has been cooped up for a while now.” 
 
 Chicago resident Matt Quilty, 43, was there with his two daughters, Ella, 6, and Cora, 3. 
 
 “We are all getting cabin fever,” Quilty said. “School is closed again, and we just wanted to get out and do something. We might be back here tomorrow again.” 
 
 But not everyone was eager to be outside. 
 
 Gina Brown, 28, expressed that sentiment as she trudged through Monday morning’s harsh winds and low temperatures to make it to her job in Hyde Park on Monday. 
 
 “If we can be brave enough to come out in this weather, why can’t we be brave enough to just take a day off?” Brown, 28, asked as she pontificated about the cold, still wearing her coat and scarf indoors. “I really can’t wrap my mind around why people want to be outside. What do you need so badly when it’s 20 below zero? A protein shake? Lip balm?” 
 
 As Chicago-area residents braced themselves for a second day of deadly cold, public officials and leaders grappled with keeping the city running during this year’s second subzero freeze. Officials with the Adler Planetarium announced they would close their facility Tuesday and the Museum of Science and Industry would close that day too. 
 
 Officials with CPS decided early on to keep schools shuttered an extra day. 
 
 “We will continue to put the safety of our students and families first,” said CPS CEO Barbara Byrd-Bennett. “This historic stretch of dangerously cold weather has forced the District to remain closed until we are confident that students can return to school safely.” ||||| Story highlights Plane slides off taxiway in Chicago; nobody hurt 
 
 Weather blamed for at least 13 deaths 
 
 Nights in Plains states could get to 30 below zero 
 
 Wind chills will drop to minus 50 in some places; frostbite can strike quickly 
 
 Get ready for bone-chilling cold you probably haven't endured in years. 
 
 A deep freeze is spreading across much of the United States this weekend, making the nor'easter that just blanketed about 20 states with snow look like a mere curtain raiser. 
 
 Sunday temperatures are expected to hit 30 degrees below zero in North Dakota and other sections of the Plains and Midwest; the wind chill will make it feel like minus 50, the National Weather Service said. 
 
 By Wednesday, nearly half the nation -- 140 million people -- will shiver in temperatures of zero or lower. 
 
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 The arctic blast threatens to sweep subzero lows as far south as Alabama and plunge much of the Deep South into the single digits. 
 
 Winter weather in the past week has claimed at least 13 lives, CNN has confirmed. 
 
 Eleven people died in road accidents -- including one man crushed as he was moving street salt with a forklift. 
 
 A man in Wisconsin died of hypothermia. And in Byron, New York, a 71-year-old woman with Alzheimer's disease wandered away from her home Thursday night and was found dead in the snow in a wooded area about 100 yards away. 
 
 in Chicago, a plane headed to Las Vegas slid off the taxiway at O'Hare International Airport on Saturday night. None of the customers on Spirit Flight 245 were injured, said Misty Pinson, director of corporate communications for Spirit. 
 
 Opening act 
 
 The cold blast burst onto the stage in the Northern Plains States early Saturday, hurling North Dakota into below-zero territory. 
 
 Minnesota has already closed schools on Monday. 
 
 "I have made this decision to protect all our children from the dangerously cold temperatures," Gov. Mark Dayton said. 
 
 People in the town of town of Embarrass, Minnesota, say they may break their cold temperature record of 64 below, set in 1996. 
 
 "I've got a thermometer from the weather service that goes to 100 below," resident Richard Fowlei told CNN affiliate KQDS . "If it gets that cold I don't want to be here." 
 
 Chicago native Leo Londono, 30, said this is the harshest winter he's experienced in the city. From his apartment, he can see large chunks of ice floating on Lake Michigan. 
 
 "It's so cold you don't want to step outside," he said. "There's wind chill. And then this huge Arctic air blast is supposed to come through and I don't want to even leave my home." 
 
 The low temperatures and wind chill are a recipe for rapid frostbite or hypothermia. 
 
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 A 66-year-old man died of hypothermia in Milwaukee on Friday, the medical examiner's office said. 
 
 The weather service's Twin Cities, Minnesota, office warns, "Exposed flesh can freeze in as little as five minutes with wind chills colder than 50 below." 
 
 This system will produce "the coldest air in two decades," the service said. 
 
 The danger of injury and death from the cold will spread with the cold front into the Midwest by Monday night. 
 
 Power outages were not as widespread despite blizzard-level winds in some places when the nor'easter passed through in the last few days. 
 
 Indiana Gov. Mike Pence encouraged residents to do more than check on friends and relatives. 
 
 "In preparation for the inclement weather, I encourage Hoosiers to assemble an emergency preparedness kit with plenty of non-perishable food and water, fill any necessary prescriptions, ensure they have a safe heating source, avoid unnecessary travel and be careful if they must be outside." he said. 
 
 Upper Midwest 
 
 Sunday night in Chicago will see a shivering 16 to 20 below zero and -- once you factor in the Windy City's stiff breeze -- a chill of 35 below to 45 below zero. 
 
 Lambeau Field in Green Bay, Wisconsin, is unfortunately not a domed stadium. Fans and players there will be outdoors and brave temperatures approaching minus 20 as the Packers battle the San Francisco 49ers for a chance to advance to the Super Bowl. 
 
 Some sportswriters speculated that it may go down in the record books as the coldest football game ever played. 
 
 The Packers organization and a stadium vending company will serve free hot chocolate and coffee to help fans withstand the deep freeze. 
 
 As Packers head coach Mike McCarthy said Friday: "This is not the norm." 
 
 That's is not the only game where fans will brave the freeze. 
 
 On Saturday in Philadelphia, the hometown Eagles hosted the New Orleans Saints in a playoff game. Temperatures were in the mid-20s at kickoff. 
 
 Marching on 
 
 As the arctic cold conquers about half of the continental United States, temperatures are forecast to dip into the minus teens through the lower Midwest. Snow will cover swaths from the Plains to the Ohio and Mississippi River Valleys, all the way to New England. 
 
 Parts of the Midwest could see temperatures not recorded in 15 to 20 years -- for a painful couple of days. 
 
 Even areas as far south as Nashville could be frozen solid in zero-degree cold as the arctic air mass dives southward at the beginning of next week. 
 
 Flight madness 
 
 Thousands were stuck at airports nationwide Friday because of systemwide delays -- though at least they are not out in the frigid cold. 
 
 Lesley Ryland tried to get home to England after attending her son's wedding in Kentucky. 
 
 "I was supposed to fly from Kentucky/Louisville up to New York, but flights have been canceled at New York, so instead I've come here," Ryland told CBS Atlanta, a CNN affiliate. "Hopefully tonight, I'll get a transfer from here back over to London." 
 
 FlightAware.com, which tracks cancellations due to weather and mechanical problems, said about 3,200 flights were canceled Friday within, into or out of the United States. 
 
 Expect more of the same in the coming days. At 10 p.m. Saturday, 1,391 flights had been canceled. About 760 Sunday flights have already been called off. 
 
 Though the temperature in Las Vegas was 52 degrees -- above zero -- passengers there were also feeling the winter's sting Friday. 
 
 Long lines formed inside McCarran International Airport at the counters for Southwest Airlines, which had canceled many of its flights to and from Chicago. The airline carries 40% of Las Vegas' passengers, according to Chris Hayes, an airport spokesman.
– Baby, it's so cold outside that the AP is throwing around the term "polar vortex," which is apparently "a counterclockwise-rotating pool of cold, dense air"—and it's got more than half the US wrapped in its icy clutches. It's not going anywhere anytime soon: The frigid temps are looking to hang out into tomorrow and Tuesday. A look around at the coldness: The mercury hit negative 31 in International Falls, Minn., negative 21 in Duluth, Minn., and 9 below in Bismarck, ND. Wind chills of 70 below are still within the real of possibility. Parts of Missouri and Illinois could get up to a foot of snow; the former is "experiencing thunder snow and whiteout conditions," according to a MoDOT spokeswoman. Thousands of flights have been delayed in the Midwest and Northeast, AccuWeather reports. Flight delays at Boston's Logan International Airport could last "days, not hours," said a Jet Blue Airways spokeswoman, the Boston Globe reports. Minnesota has canceled school tomorrow for the entire state. In Wisconsin, Milwaukee and Madison have done likewise. In Green Bay, today's playoff game between the Packers and the 49ers could prove a little chilly for the visiting team: The temperature at kickoff is supposed to be negative 2. The AP notes that doctors are advising fans to drink warm fluids that are not of the alcoholic variety. And of course, this happened at JFK Airport, which has since re-opened.