Updated 7:45 p.m.

Extremely cold, possible record-breaking temperatures gripped the Chicago area Tuesday after a powerful snowstorm hit the region overnight Monday. Forecasters are describing the subzero weather the next three days as potentially life-threatening.

Subzero temperatures will begin Tuesday night, but Wednesday is expected to be the worst. Wind chills in parts of northern Illinois could fall to negative 55 degrees.

If there’s a day where one needs to demonstrate cold weather safety to the max, it is Wednesday. The Arctic air will be fully entrenched. Temperatures remain in negative double digits for most areas the entire day. Wind chills -40° to -55°. #ILwx #INwxhttps://t.co/d9uKYzeUsQ pic.twitter.com/LVAWtRidxX

— NWS Chicago (@NWSChicago) January 29, 2019

The cold air arrived in Chicago overnight, plunging temperatures to one degree Tuesday morning. The wind chill made it feel like 19 degrees below zero, according to the National Weather Service. 

The overnight low temperature will be negative 21, and the high temperature Wednesday is forecast to be a frigid 13 below zero. 

Temperatures will drop to 24 below zero Wednesday night. That would be close to Chicago’s record low temperature at O’Hare International Airport: 27 degrees below zero in 1985.

Illinois Gov. JB Pritzker said the State Emergency Operations Center is enacting an emergency preparedness plan. He called the weather forecast for Tuesday through Thursday “potentially historic.”

Northeast Illinois is under a wind chill warning from 6 p.m. Tuesday until noon Thursday.

School’s out, from kindergarten to college

Public and private schools across the Chicago region canceled classes due to the cold on Wednesday and Thursday. The Emergency Closing Center maintains a list.

On Tuesday night, Chicago Public Schools officials said classes would be canceled for a second day on Thursday. They had already announced plans to keep students home on Wednesday.

The Archdiocese of Chicago, which oversees 217 parochial schools in the city and suburbs, was letting principals decide whether to hold classes Wednesday, but a spokesperson expected most would likely be closed.

All day Tuesday, suburban school districts also announced closures, including in Palos Hills, Oak Park, Huntley, Wilmette, Skokie, Evanston, Glenview, and Franklin Park.

A few schools will close their campuses but still expect students to work at home online, including Stevenson High school in Lincolnshire and West Chicago High School.

They’re calling these “e-learning” day. Thanks to a 2017 Illinois state law, e-learning days count as an official attendance day. Teachers will share lessons digitally and students will complete the work remotely.

Most Chicago-area universities canceled classes Tuesday night through Wednesday or Thursday. This includes the University of Illinois at Chicago, Roosevelt, Northwestern, DePaul, Loyola, Columbia College, the University of Chicago, Northern Illinois, Northeastern, the City Colleges of Chicago, and the School of the Art Institute.