Forecasters describe wildly fluctuating weather trends as whiplash.
The north polar vortex has recently been known to become distorted or even split in pieces, which was the case with the 2014 polar vortex that many Midwesterners can remember.
"This morning is some of the coldest of the temperatures across the upper Midwest and we still have some unsafe wind chills", Andrew Orrison, a forecaster for the National Weather Service said. Cotton, Minnesota, had the lowest national temperature recorded early on Thursday at minus 48 C, before the weather warmed up, the weather service reported. Rockford, Illinois, was at a record-breaking minus 31 degrees (minus 35C) on Thursday morning but should be around 50 degrees (10C) on Monday.
Explaining the phenomenon, Subrath-Ali said, "The very cold air in a polar vortex is kept within the polar regions by fast-moving winds (jet streams) that surround it". By Friday morning, about 13 million were under wind chill warnings or advisories.
The bitter weather was believed to be tied to the deaths of at least eight people, including a man thought to have collapsed after shoveling snow and frozen to death in his Milwaukee garage.
By Saturday, highs will be in the 30s and even low 40s F, while the central Plains will be in the low 60s F, almost 20 to 25 degrees above normal, the weather service said. The previous record low on January 31 was -12 in 1985. But as the temperatures abruptly turn warmer, USA emergency officials warn of flooding and utility risks.
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Authorities and health experts warned of frostbite and hypothermia within minutes of exposure to the frosty air. "They are going from well below average temperature to well above average temperatures".
It said a historic low temperature for IL of -38F (-39C) had been reported in the town of Mt Carroll and was being reviewed before being declared a state record. By 2 a.m. Wednesday, Chicago had beaten that by one degree.
Amtrak train services that had been halted since Wednesday in Chicago's hub resumed yesterday, as did U.S. postal services that were halted or limited in six Midwest states.
This week's cold snap virtually shut the city down for a day, as everything from flights and public transit to the city's public school system and mail delivery in ZIP codes in Chicago and around IL was canceled for Wednesday and Thursday.
As of noon Thursday, at O'Hare International Airport 1,467 flights were canceled, according to the Chicago Department of Aviation.
According to Amtrak, all Midwest corridor services to and from Chicago are canceled on Thursday.
Metra Electric trains will not run Thursday, Metra said. Fiat Chrysler Automobiles NV canceled a shift on Thursday at two of its plants.
Just days after the arctic conditions, with temps as low as minus-56 degrees, the Midwest will seemingly swing into another season as the thermometer swings in the opposite direction by as much as 80 degrees.