MILWAUKEE (AP) — Extreme cold and record-breaking temperatures are crawling into parts of the Midwest after a powerful snowstorm pounded the region, and forecasters warn that the frigid weather could be life-threatening.
Minneapolis Public Schools officials have canceled classes through Wednesday, when the region is expected to experience frigidly low temperatures not seen in a quarter century. Hundreds of Michigan schools were closed Tuesday, including in Detroit, while Chicago Public Schools canceled Wednesday classes because of the anticipated cold snap.
"You're talking about frostbite and hypothermia issues very quickly, like in a matter of minutes, maybe seconds," said Brian Hurley, a meteorologist with the Weather Prediction Center.
Subzero temperatures will begin Tuesday, but Wednesday is expected to be the worst. Wind chills in northern Illinois could fall to negative 55 degrees (negative 48 degrees Celsius), which the National Weather Service called "possibly life threatening." Minnesota temperatures could hit minus 30 degrees (negative 34 degrees Celsius) with a wind chill of negative 60 (negative 51 degrees Celsius).
The potentially record-breaking low temperature forecast in Milwaukee is negative 28 degrees (negative 33 degrees Celsius), with a wind chill as low as negative 50 (negative 45 degrees Celsius). The current record of minus 26 degrees (negative 32 degrees Celsius) was set in 1996.
"That's 40 degrees below normal," Hurley said.
The unusually frigid weather is attributed to a sudden warming far above the North Pole . A blast of warm air from misplaced Moroccan heat last month made the normally super chilly air temperatures above the North Pole rapidly increase. That split the polar vortex into pieces, which then started to wander, said Judah Cohen, a winter storm expert for Atmospheric Environmental Research.
One of those polar vortex pieces is responsible for the subzero temperatures across the Midwest this week.
The Chicago Zoological Society said it was closing the Brookfield Zoo on Wednesday and Thursday — marking only the fourth time the zoo has closed during its 85-year history — to ensure the safety of its employees and animals. At O'Hare International Airport in Chicago, the high temperature Wednesday is expected to be negative 14 degrees (negative 25 degrees Celsius), which would break a record set on Jan. 18, 1994.
Homeless shelters were also preparing for the onslaught of cold. The Milwaukee Rescue Mission's call volume was "unusually high," but officials said there should still be enough beds for those who need them.
In Minneapolis, charitable groups that operate warming places and shelters were expanding hours and capacity "as they do whenever dangerous extreme temperature events occur," said Hennepin County Emergency Management Director Eric Waage. He said ambulance crews were handling all outside response incidents as being potentially life-threatening.
Chicago Mayor Rahm Emanuel said city agencies are making sure homeless people are in shelters or offered space in warming buses. He also urged residents to check on their neighbors and take safety precautions.
The governors in Michigan and Wisconsin have declared states of emergency ahead of the dangerously cold weather.
Cold weather advisories are in effect across a broad swath of the central U.S., from North Dakota to Missouri and spanning into Ohio. Temperatures will be as many as 20 degrees below average in parts of the Upper Great Lakes region and Upper Mississippi Valley, according to the National Weather Service.
On Monday, snowplow drivers had trouble keeping up with the snowfall in Minnesota and Wisconsin, where some areas got as much as 15 inches (38 centimeters) of snow. Chicago-area commuters woke up to heavy snowfall, with more than 5 inches (12.7 centimeters) already on the ground. In Michigan, nonessential government offices were closed, including the Capitol.
Rare snowfall was also forecast for some southern states.
Associated Press reporters Caryn Rousseau in Chicago, Gretchen Ehlke in Milwaukee and David Runk in Detroit, and AP Science Writer Seth Borenstein contributed to this report.