CHICAGO � The National Weather Service's official temperature fell to 21 degrees below zero overnight, falling short of Chicago's record low temperature of 27 degrees below zero, set Jan. 20, 1985.
Though it remains possible the temperature may get slightly colder, it won't be enough to break the all-time record, said Matt Friedlein, a meteorologist with the National Weather Service. Chicago did, however, shatter the record low temperature for Jan. 31, which was previously set in 1985 when the temperature reached 12 below.
The face-freezing weather capped a days-long polar vortex cold snap that descended on the Midwest starting Monday night. The arctic blast led to school cancellations, closed courts, thousands of flight cancellations, a stop on U.S. Postal Service delivery and disruption of all Amtrak service for a day, as well as scaled-back Metra and CTA service.
Even before Thursday morning, Chicago already had seen the lowest temperature since Jan. 20, 1985 _ 23 degrees below zero at O'Hare at 7 a.m. and 8 a.m. Wednesday, according to the weather service.
The four-day cold snap that has hit much of the Midwest and East Coast happened after a disruption in the polar vortex. One cold front moved in overnight Monday, followed by another later Tuesday, causing the high Wednesday to reach only 10 degrees below zero. The stretch of subzero temperatures was expected to last into Thursday, with the temperature at O'Hare possibly not rising to about zero until early Friday.
The daily record low for Jan. 30 of minus 15 fell early Wednesday and the record low for Jan. 31 of minus 12 was bested as soon as the day started, according to the weather service.
"Lows early Thursday morning will be in the (minus) 20s to (minus) 30s across the area," according to a weather service bulletin. "Some isolated readings of around 40 (below zero) are possible west of the Fox Valley in Illinois."
Temperatures were expected to rise above zero just after midnight Thursday, finally inching above freezing sometime Saturday morning.
