Arctic freeze warms after leaving 21 dead READ MORE

Predicted near-surface air temperature differences from normal relative to 1981-2010. <a rel=

Predicted near-surface air temperature differences from normal relative to 1981-2010. Pivotal Weather CC BY-ND

Among the dead are an 18-year-old University of Iowa student; four men found frozen in Illinois, Wisconsin and MI; six Iowans who died in vehicle crashes; a pedestrian hit by a snowplow in Illinois; and a woman found frozen in her apartment in Milwaukee after a "thermostat malfunction", the Times reports.

"They are life-threatening temperatures, and they should be treated accordingly", Chicago Mayor Rahm Emanuel cautioned residents Wednesday evening. At the time Belz was discovered, the air temperature was -22, with a wind chill of -51.

"That cold air that was over the Great Lakes, over the Midwest, has shifted off", said Bryan Jackson, a National Weather Service meteorologist, according to ABC.

Scientists call these "sudden stratospheric warming" events, when a continent-sized chunk of rapidly sinking air (usually over Eurasia) quickly heats up and disrupts the polar circulation, sometimes completely disintegrating it. Statistically, that's when the cold air floodgates can really open as the jet stream scrambles to contain the chaotic swirls of polar air that descend southward in the aftermath.

The death toll rose from a previous 12 after at least nine more people in Chicago were reported to have died from cold-related injuries from 2019 polar vertex, according to Dr Stathis Poulakidas at the city's John H Stroger Jr Hospital.

Cable worker Brian Stachovic said he was up an electrical pole for only five minutes on Thursday before his fingers and toes went numb, and he had to go inside to avoid frostbite.

Homeless and displaced people were particularly at risk.

For the second day in a row, the intense cold and windy conditions forced U.S. airlines to cancel more than 2,000 flights.

Check out two stories on page three that will help you stay safe and warm during cold weather, and give you some tips on using space heaters and keeping your pipes from freezing. Thousands of flights were scrapped this week, especially at Chicago's two major airports, which experienced more than 1,500 cancellations a day.

More than 30 record lows were shattered across the Midwest.

Temperatures from southern New England to the Upper Midwest should climb back up to the mid-40s to low 50s Fahrenheit (4 to 10 degrees Celsius) through the weekend and Monday, forecasters said.

The lowest temperature recorded early yesterday morning was -37C in Stonington, Michigan, according to the National Weather Service.

The icy cold is expected to loosen its grip on Friday. "Here we are going right into spring-like temperatures".

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