Ready or not, sub-freezing temps forecast for Tuesday night, Wednesday morning

The first freezing temperatures of the seasons are expected to roll in Tuesday night and Wednesday morning for a large portion of northwest Illinois, the Nation Weather Service reports.

A freeze watch with sub-freezing temperatures is in effect starting late Tuesday night for McHenry, DeKalb, La Salle, Lee, Ogle, Grundy, Kane, Kendall, Winnebago, Livingston and Boone counties.

Widespread frost is expected to coat the area from around 2 a.m. to 9 a.m. Wednesday morning with lows ranging from about 30 degrees in McHenry County to as low as 27 degrees in Ogle County, NWS Meteorologist Kevin Doom said. During the Wednesday, it’s forecasted to be sunny and warm up to seasonal temperatures of mid-50s.

“We have a storm system that’s pushing over the area right now and that’s going to spill a ton of cold air over the region,” Doom said.

Another widespread frost could hit from 4 to 8 a.m. Thursday. From there, temperatures are expected to shoot back to the mid-60s, with nighttime lows in the 40s for the rest of the week, Doom said.

The frost should affect roads because there won’t be any freezing precipitation, but plants and crops could be killed and unprotected outdoor plumbing could get damaged, according to the NWS. Doom advises to bring any plants inside or protected in a greenhouse.

“Plants are in jeopardy of freezing,” he said. “The growing seasons for sure looks to come to an end after about Thursday.”

The first freezing temperatures of the season are in line with last year’s low of 32 degrees on Oct. 11, 2023, Doom said.