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The US is currently experiencing historically cold weather , with Chicago dropping to a low of around -23F (-30C) on Wednesday – but what is the cause of this extreme drop in temperature?
A split in the polar vortex has been identified as the cause of the bitter cold that continued to sweep parts of the country on Thursday.
The polar vortex is a mass of cold air that usually stays bottled up in the Arctic.
But when the split occurred, that air spilled and traveled much further south than usual, causing a painfully cold weater system that put much of the Midwest into a historic deep freeze .
Temperatures still tumbled to record lows in some places on Thursday, though the weather was expected to start easing into Friday.
Polar vortex brings temperatures colder than Antarctica to the USShow all 52 1 /52Polar vortex brings temperatures colder than Antarctica to the US Polar vortex brings temperatures colder than Antarctica to the US Chicago Ice covers the Lake Michigan shoreline
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Polar vortex brings temperatures colder than Antarctica to the US Minnesota A firefighter walks past an ice-encrusted home after an early morning house fire
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Polar vortex brings temperatures colder than Antarctica to the US Ontario People walk in a park on the US side of Niagara Falls
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Polar vortex brings temperatures colder than Antarctica to the US Massachusetts Mike Calen, left, and Steve Goyette, right, prepare to tie off as the ice covered fishing boat, Buzzards Bay, arrives at New Bedford harbour
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Polar vortex brings temperatures colder than Antarctica to the US Pedestrians protecting their faces from the cold in New York City, in Washington DC, along Lake Michigan's ice covered shoreline, in the Brooklyn borough of New York, in Chicago, in Kingston, Ontario, and in Montreal
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Polar vortex brings temperatures colder than Antarctica to the US Chicago Snow and ice covers Soldier Field
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Polar vortex brings temperatures colder than Antarctica to the US Chicago Gas-burning heaters are placed on railroad tracks as Metra commuter train passes by
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Polar vortex brings temperatures colder than Antarctica to the US Chicago Ice builds up along the shore of Lake Michigan
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Polar vortex brings temperatures colder than Antarctica to the US Ontario A tree is covered in ice from the mist at park beside the falls in Niagara Falls
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Polar vortex brings temperatures colder than Antarctica to the US Minneapolis Water vapor rises above St. Anthony Falls on the Mississippi River beneath the Stone Arch Bridge
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Polar vortex brings temperatures colder than Antarctica to the US Massachusetts Ice flows fill the Merrimack River as it heads towards the Atlantic Ocean in Newburyport
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Polar vortex brings temperatures colder than Antarctica to the US Ontario A tourists take pictures of the Canadian Horseshoe falls in Niagara Falls
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Polar vortex brings temperatures colder than Antarctica to the US Minneapolis Sub-zero temperatures produce icicles that hang from a restaurant
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Polar vortex brings temperatures colder than Antarctica to the US Ontario A person takes a selfie beside on the US side of Niagara Falls
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Polar vortex brings temperatures colder than Antarctica to the US
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Polar vortex brings temperatures colder than Antarctica to the US Minneapolis Water vapor from the Mississippi River envelopes a bridge as sub-zero temperatures produce dangerous windchills
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Polar vortex brings temperatures colder than Antarctica to the US New York Pedestrians walk through the falling snow in the Financial District
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Polar vortex brings temperatures colder than Antarctica to the US Ontario Steam rises from the US Niagara Falls before sunrise
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Polar vortex brings temperatures colder than Antarctica to the US Chicago Snow covers Wrigley Field entrance
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Polar vortex brings temperatures colder than Antarctica to the US New York Workers shovel at the entrance to City Hall in whiteout conditions
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Polar vortex brings temperatures colder than Antarctica to the US NASA's 'Blue Marble' data set of weather systems over the continental United States
US National Oceanic and Atmospheric Administration/EPA
Polar vortex brings temperatures colder than Antarctica to the US Chicago Ice and snow builds up along Lake Michigan
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Polar vortex brings temperatures colder than Antarctica to the US Minneapolis
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Polar vortex brings temperatures colder than Antarctica to the US Minneapolis Chuck Carpenter is frost covered as he goes for a walk
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Polar vortex brings temperatures colder than Antarctica to the US Chicago A man walks along the lakefront as temperatures hovered around -20 degrees
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Polar vortex brings temperatures colder than Antarctica to the US Chicago Frozen Chicago River
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Polar vortex brings temperatures colder than Antarctica to the US New York A man walks next to a subway train as heavy snow falls
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Polar vortex brings temperatures colder than Antarctica to the US Chicago A digital board shows flight cancellations at Terminal 3 at O'Hare International Airport
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Polar vortex brings temperatures colder than Antarctica to the US Chicago
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Polar vortex brings temperatures colder than Antarctica to the US Chicago A shirt that was hung is seen frozen
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Polar vortex brings temperatures colder than Antarctica to the US Chicago People walk along the lakefront
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Polar vortex brings temperatures colder than Antarctica to the US New York A young man waits on a subway platform in freezing temperatures
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Polar vortex brings temperatures colder than Antarctica to the US Chicago Mist rises from the city and Lake Michigan
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Polar vortex brings temperatures colder than Antarctica to the US New York People walk through the snow in lower Manhattan
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Polar vortex brings temperatures colder than Antarctica to the US Chicago The James Versluis breaks ice on the frozen Chicago River near Navy Pier
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Polar vortex brings temperatures colder than Antarctica to the US Michigan
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Polar vortex brings temperatures colder than Antarctica to the US Minneapolis
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Polar vortex brings temperatures colder than Antarctica to the US Chicago
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Polar vortex brings temperatures colder than Antarctica to the US New York
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Polar vortex brings temperatures colder than Antarctica to the US Chicago
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Polar vortex brings temperatures colder than Antarctica to the US Chicago
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Polar vortex brings temperatures colder than Antarctica to the US Michigan
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Polar vortex brings temperatures colder than Antarctica to the US New York
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Polar vortex brings temperatures colder than Antarctica to the US Chicago
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Polar vortex brings temperatures colder than Antarctica to the US New York
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Polar vortex brings temperatures colder than Antarctica to the US Chicago
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Polar vortex brings temperatures colder than Antarctica to the US Minneapolis
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Polar vortex brings temperatures colder than Antarctica to the US Chicago
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Polar vortex brings temperatures colder than Antarctica to the US Chicago
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Polar vortex brings temperatures colder than Antarctica to the US Chicago
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Polar vortex brings temperatures colder than Antarctica to the US Chicago
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Polar vortex brings temperatures colder than Antarctica to the US Chicago
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Record-breaking cold hit northern Illinois early Thursday, when the temperature in Rockford dropped to -30F (-34C). The previous record in the city, northwest of Chicago, was -27F (-33C) on 10 January, 1982.
The blast of polar air that enveloped much of the Midwest on Wednesday closed schools and businesses and strained infrastructure with some of the lowest temperatures in a generation. The deep freeze snapped rail lines, canceled hundreds of flights and strained utilities.
A man walks along an ice-covered break-wall along Lake Michigan while temperatures were hovering around -20F (-29C) on 31 January, 2019 in Chicago, Illinois. (Photo by Scott Olson/Getty Images) ((Photo by Scott Olson/Getty Images)) Chicago dropped to a low of around -23F (-30C), slightly above the city's lowest-ever reading of -27F (-32C) from January 1985. Milwaukee had similar conditions. Minneapolis recorded -27F (-32C). Sioux Falls, South Dakota, saw -25F (-31C).
Wind chills reportedly made it feel like -50F (-45C) or worse.
Support free-thinking journalism and attend Independent events At least twelve people have died in weather-related circumstances. Some died in weather-related traffic accidents, others from apparent exposure to the elements.
Additional reporting by agencies.
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