A deadly and likely once-in-a-lifetime arctic deep freeze from the polar vortex settled in over the Midwest on Wednesday, shuttering schools and causing the U.S. Postal Service to suspend mail delivery in areas as forecasters warned people to keep their mouths closed if stepping out.

Wind chills of negative 54 degrees Fahrenheit were reported in International Falls, Minnesota and minus 52 degrees in Minneapolis on Wednesday morning while Des Moines, Iowa reported a bitterly cold wind chill of minus 42 degrees and Chicago had a wind chill of negative 52 degrees just before sunrise.

"The heart of the Arctic cold has arrived," the National Weather Service's Chicago office said on Twitter. "The combined effects of the cold & winds are at their peak today with wind chills of -45° to -60° continuing. The afternoon highs today...yes the highs...will only be -11° to -17°."

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The cold snap also is causing travel disruptions throughout the region. United Airlines canceled about 500 flights at Chicago's O'Hare International Airport from Tuesday through Thursday, while Southwest Airlines canceled more than 700 flights at Midway International Airport in the same time period. Amtrak also canceled all trains out of Chicago on Wednesday and into Thursday.

The temperatures across the Midwest on Wednesday were colder than the likes of Greenland and Alaska. The temperatures in the Midwest were colder than at the McMurdo Station, the main U.S. station in Antarctica, where it was a balmy 23 degrees on Wednesday. A wind chill of minus 25 degrees can freeze skin within 15 minutes, according to the National Weather Service.

The cold air will continue to blanket the region on Wednesday into Thursday, with some areas possibly reaching a minus 70-degree windchill overnight, Fox News Senior Meteorologist Janice Dean said on "FOX and friends."

"The Midwest and Great Lakes are well into this Arctic blast, with dangerously low wind chills widespread across the region this morning," Dean said. "Air temperatures are well below zero, in the -10s to -30s for many. Wind chills of -20 to -70 will continue through early Thursday flirting with all-time record lows ever recorded."

"You really can't be outside for longer than minutes because your face will freeze in these type of temperatures," she added.

COLD TURNS DEADLY

The bitter blast blanketing the Midwest has already taken a deadly turn after a 55-year-old man was found frozen in a garage in Wisconsin on Tuesday and two people dead in Michigan.

The Milwaukee County Medical Examiner’s Office told FOX6 that Charley Lampley collapsed and died after shoveling snow at his home in Milwaukee.

Lampley was found frozen in a detached garage near a snow shovel and had appeared to have had been outside overnight. The garage door was open, and the medical examiner noted Lampley was fully clothed and dressed for the weather.

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The preliminary manner of death was ruled “natural," according to FOX6.

In Michigan, the frozen body of a 70-year-old man was discovered Wednesday morning in Detroit where temperatures dipped to negative 6 degrees.

Detroit Police had received a call around 2 a.m. Wednesday on a missing person, but were unable to find the man at the time, FOX2 reported. The man's body was discovered about six hours later, police said.

A former Ecorse city council member was also found dead outside of his home after being exposed to the elements. The Ecorse Police Department told FOX2 the man, who is in his 70s, died from exposure to the elements.

Police are investigating the death as weather-related, but would not provide further information. The identity of the man had yet to be released. At least three other deaths were linked to the weather system Tuesday, including a man struck and killed by a snow plow in the Chicago area and a young couple whose SUV struck another on a snowy road in northern Indiana.

"THIS IS NOT A CASE OF 'MEH, IT'S IOWA DURING WINTER AND THIS COLD HAPPENS'"

Forecasters in Iowa took the extra step of emphasizing how cold conditions will be to hardy Midwesterners by telling people something blunt: keep your mouths shut outdoors.

The Des Moines office of the National Weather Service said in its forecast discussion on Tuesday that the arctic air will be the "coldest air many of us will have ever experienced."

"These are record-breaking cold air temperatures, with wind chill values not seen in the 21st century in Iowa," the agency said.

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Forecasters told people planning on going outside to make sure they cover any exposed skin and make sure they have supplies in their cars.

"Further, make sure your mouth is covered to protect your lungs from severely cold air," the NWS said. "Avoid taking deep breaths; minimize talking."

EMERGENCY DECLARATIONS, SHELTERING IN PLACE.

Governors in Illinois, Wisconsin and Michigan declared emergencies as the worst of the cold threatened on Wednesday, as hundreds of public schools and several large universities from North Dakota to Pennsylvania canceled classes.

Major attractions in Chicago, including the Lincoln Park Zoo, Art Institute and Field Museum, weren't opening Wednesday. Chicago officials were turning buses into mobile warming shelters to encourage homeless people to come in off the streets

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"These (conditions) are actually a public health risk and you need to treat it appropriately," Chicago Mayor Rahm Emanuel said Tuesday. "They are life-threatening conditions and temperatures."

The U.S. Postal Service said it would suspend mail delivery on Wednesday in parts or all of several Midwest states including North and South Dakota, Nebraska, Kansas, Minnesota, Wisconsin, Iowa and Illinois.

The Associated Press contributed to this report.