By RYAN GORMAN
The arctic air mass sitting over America's second-largest city has set Twitter ablaze even as residents are shivering in single digit temperatures.
The so-called polar vortex that descended on Chicago this week has sent temperatures crashing below zero at night, with wind chills approaching 30-below, and led Chicagoans to compare the windy city to Siberia.
A search on Twitter for the #Chiberia hashtag revealed pictures of a frozen Lake Michigan, near white-out conditions during a Thursday afternoon snow squall and also of ice accumulating against a coffee shop window -- on the inside.
Temperatures reached only the single digits on Thursday, but wind chills still made it feel like 25-below, according to the Chicago Tribune.
The dangerous cold caused hundreds of school districts to cancel classes for the fourth straight day.
Striking images from earlier in the week showed steam rising off Lake Michigan and the Chicago River. Ice flows have since begun to freeze over in more shallow depths.
West Chicago took home the bacon Thursday with a low temperature of minus 11, several neighboring towns dropped to minus 10.
Temperatures earlier in the day at O'Hare International Airport hit minus 8, which somehow was not a record low. That honor goes to the minus 11 felt on this date in 1942.
The polar air mass responsible for the bitter cold originated last week at the North Pole and quickly moved south, according to NOAA.
The cold air has been slowly moving east and resulted in a low temperature Thursday morning of minus-38 degrees in Estcourt Station, the northernmost town in Maine.
Adding to the misery, three inches of powdery snow expected Thursday is causing problems with Metra commuter rail trains, the agency said.
The Red Line, part of the city's famed El-train network, was also snarled when doors were unable to close after freezing open, according to the CTA.
Friday is expected to be similar, with highs only into the low single digits, but Chicagoland should begin to thaw out by next week, according to forecasters
Temperatures should claw their way back into the mid-30s by Monday.