(CNN) - If you think it's cold now, just wait.
The deep freeze gripping much of the country is about to send temperatures plummeting to unbelievable lows.
Parts of the Midwest and Great Plains will plunge as low as 30 degrees below zero on Sunday. That's where the Green Bay Packers will host the San Francisco 49ers in what could be the coldest football game in NFL history.
By Wednesday, nearly half the nation -- 140 million people -- will shudder in temperatures of zero or lower, forecasters said. Even the Deep South will endure single-digit or sub-zero temperatures.
Here's what to expect across the country:
The central U.S. ... and one freakishly cold game
As if the 30-below-zero temperatures weren't frigid enough, the wind chill in much of Midwest and Great Plains could drop to minus 50, the National Weather Service said. And that's on top of the moderate to heavy snow possible over the Great Lakes and Ohio Valley on Sunday.
"Brutal conditions will continue pushing southeastward to the Ohio Valley and Mid-South by Monday, and to the Northeast and Mid-Atlantic by Tuesday," the weather agency said. "Afternoon highs on Monday for parts of the Midwest states and the Ohio Valley will fail to reach zero degrees."
More than 70,000 hardcore Packers fans hoping to see their team get closer to the Super Bowl will have their loyalty tested Sunday as they endure temperatures as low as 15-below-zero in Green Bay, Wisconsin. With the wind, the air could feel as cold as minus-30 to minus-40 degrees to the sold-out crowd.
Those conditions could trump the 1967 "Ice Bowl" -- also at Green Bay -- when the temperature was 13-below zero. The open-air stadium was so cold that referees couldn't sound their whistles and trumpet players got their instruments stuck to their lips.
The Packers will give free hand warmers, hot chocolate and coffee to the fans braving the cold on Sunday, spokesman Aaron Popkey said.
In Embarrass, Minnesota, residents wondered whether they might see their record-cold temperature 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 Fowlei told CNN affiliate KODS. "If it gets that cold, I don't want to be here."
The Deep South
The arctic blast threatens to sweep subzero lows as far south as Alabama and plunge much of the Deep South into the single digits.
To put things in perspective, the weather in Atlanta on Monday will be colder than in Anchorage, Alaska, CNN meteorologist Pedram Javaheri said.
Freezing rain is also possible along the Appalachians all the way up to New England over the next couple of days, the National Weather Service said.
The low temperatures and wind chill are a dangerous recipe for rapid frostbite or hypothermia.
"Exposed flesh can freeze in as little as five minutes with wind chills colder than 50 below," the National Weather Service's Twin Cities office in Minnesota said. Forecasters there warned of "the coldest air in two decades.
Over the past week, at least 13 people have died from weather-related conditions.
Eleven people died in road accidents -- including one man crushed as he was moving street salt with a forklift.
One man in Wisconsin died of hypothermia. And an elderly woman with Alzheimer's disease in New York state wandered away from her home and was found dead in the snow in a wooded area about 100 yards away.
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 nonperishable 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.
The already dreadful stream of stranded passengers and canceled flights will only get worse.
FlightAware.com, which tracks cancellations due to both weather and mechanical problems, said more than 1,500 flights have been canceled for Sunday. That's after 4,500 flights were called off on Friday and Saturday.
In Chicago, a plane headed to Las Vegas slid off the taxiway at O'Hare International Airport on Saturday night. None of the passengers on Spirit Flight 245 were injured, an airlines spokeswoman said.
But with the Windy City inundated by snow, O'Hare will have more troubles Sunday. About 1,000 inbound or outbound flights have already been canceled, according to FlightAware.com.
This too shall pass
If there's any good news about the biting cold snap, it's that much of it should be over for the Midwest by Wednesday, the National Weather Service said.
In the meantime, those in the western third of the country can skip all the fuss. Most of the West can expect relatively pleasant weather through Monday.