(CNN) — The brutally cold weather that’s killed 11 people and trapped millions in a historic deep freeze will finally let up by week’s end — but not before a treacherous encore.

The extreme cold is more widespread Thursday as frigid air and dangerous wind chills stretch from the Upper Midwest all the way to Maine, CNN meteorologist Dave Hennen said.

More than 216 million people face freezing weather Thursday, including 84 million dealing with sub-zero temperatures.

But the misery will slowly melt away Friday, with a warming trend that could give many Americans thermal whiplash.

“Today is the last of the extreme cold air,” Hennen said Thursday. “Temperatures will rebound quickly over much of the area that saw the extreme cold, creating a yo-yo effect of extreme temperature difference.”

Chicago, for example, will see a temperature rise of almost 75 degrees — from extreme cold of 20-25 below zero to temps in the low 50s on Monday.

And Atlanta, which has shivered in the 20s this week, will enjoy temperatures in the 60s when it hosts the Super Bowl on Sunday.

Chicago might be hit with ‘frost quakes’

Across the country, the bone-chilling weather has shattered dozens of records.

Chicago came close to breaking its record of 27 below zero when temperatures plunged to 21 below, Hennen said.

But the Windy City now has something other than a negative-41 wind chill to worry about: frost quakes.

Some Chicagoans were startled awake Wednesday by a series of large booms, CNN affiliate WGN reported.

“I thought I was crazy! I was up all night because I kept hearing it,” Chastity Clark Baker said on Facebook, according to WGN. “I was scared and thought it was the furnace. I kept walking through the house. I had everyone’s jackets on the table in case we had to run out of here.”

That boom was probably a weather phenomenon known as cryoseism — and dubbed a “frost quake.” It happens when water underground freezes and expands, causing soil and rock to crack.

11 deaths are now linked to brutal weather

As millions grapple with frigid temperatures, at least 11 deaths have been linked to this week’s extreme weather.

The latest reported death was in Michigan, where the body of a 70-year-old man was found frozen near his Detroit home, police said. It was not clear why he was outdoors.

Officials in Iowa said there have been four deaths there this week, including the discovery Wednesday of a University of Iowa student.

The student, a sophomore, was found unresponsive about 4 a.m. ET behind a campus recreational facility. The temperature in Iowa City at that time was about 21 below zero, and it had been below zero all day, the National Weather Service reported.

Storm-related deaths were also reported in Illinois, Minnesota, Indiana and Wisconsin, authorities said.

Mail service is still suspended

The massive cold snap has also frozen some mail and blood donation services.

The US Postal Service said due to arctic temperatures, Thursday deliveries are suspended in parts of Illinois, Indiana, Michigan, Ohio, Pennsylvania and Wisconsin.

The American Red Cross said 370 blood drives across the country were canceled as temperatures dropped.

“The Red Cross currently has an emergency need for blood and platelet donors of all types to help ensure lifesaving medical treatments and emergency care are not delayed or canceled this winter,” spokeswoman Stephanie Rendon said in an email.

State government offices in Michigan are closed for a second day on Thursday due to “emergency weather conditions.”

Michigan wants residents to weather storm on less heat

Despite the frigid temperatures, Michigan’s governor is asking some residents to turn their heat down.

A fire at Consumers Energy’s Ray Natural Gas Compressor Station in Macomb County — which is responsible for about one-fifth of the state’s natural gas storage supply — shut down all gas flow from the facility.

With gas delivery inhibited, Gov. Gretchen Whitmer made a late-night appeal Wednesday to residents of the lower peninsula, asking them to turn their thermostats down to 65 degrees or lower until noon Friday.

It’s important for Michiganders to follow through, Whitmer said, “so that we can get through this storm with minimal harm.”

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