(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 down 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."

Hardcore Packers fans hoping to see their team advance to the Super Bowl will have their loyalty tested Sunday when more than 70,000 endure the minus-30-degree wind chill in Green Bay, Wisconsin.

Those conditions could trump the 1967 "Ice Bowl" -- also at Green Bay -- when temperature was 13-below zero and the wind chill was minus-48 degrees. The open-air stadium was so cold that 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 Richard Fowlei told CNN affiliate KQDS. "If it gets that cold, I don't want to be here."

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.

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.

Deadly conditions

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.

Travel nightmares