Near-record, unseasonable warmth will persist in the Chicago area Monday and Tuesday, weather officials said, with daytime highs likely to reach the upper 80s both days.
“(It) would be, actually, slightly above normal for mid-July, the peak of summer — so, really unusual for October,” said Gino Izzi, senior meteorologist with the Chicago office of the National Weather Service.
The normal high temperatures for this time of year are between 64 and 65 degrees, and the normal temperature averages between 55 and 56 degrees, according to National Weather Service historical data. The record high temperature for Oct. 12 was 84 degrees in 2008, and for Oct. 13, it was 88 degrees in 1975.
Monday’s official forecast for O’Hare International Airport, the weather service’s official reporting site, includes a high of 86, Izzi said.
“So, if we hit that, we’ll break the record by a couple of degrees,” he said.
The forecast for the Chicago area follows an unseasonably hot Saturday and a relatively cooler — but still warmer than usual — marathon day Sunday. Izzi said O’Hare recorded a high of 80 on Saturday and a high of 78 on Sunday.
“There was variability across the region because the winds were coming in off of the lake,” he said about Sunday. “So closer to the lakefront, temperatures (were) generally in the upper 60s to around 70 degrees.”
Other parts of the state can also expect similarly near-record or record-breaking temperatures Monday and Tuesday, according to local forecast offices.
The St. Louis office, which also covers parts of southwestern and west central Illinois beyond Missouri, said Sunday that Columbia — some 120 miles west of St. Louis — had broken a record high for the day of 91 degrees as of 3 p.m.
Rain is possible Tuesday night in northeastern Illinois as a cold front moves in, bringing cooler, more “typical mid-October” weather for the rest of the work week, with highs in the mid-60s to the mid- and upper 70s. More rain is possible Thursday.
Trends in recent decades point to an overall warming of average temperatures in winter as well as fall, spring and summer, from human activities such as fossil-fuel burning that release heat-trapping gases into the atmosphere.
In Chicago, fall is the second fastest-warming season after winter, according to climate science nonprofit Climate Central.
An analysis from the organization found that as of 2025, Chicago was experiencing 15 more fall days with higher-than-normal temperatures compared with 1970, while average autumn temperatures have increased by 2.8 degrees in that same time span. It mirrors a 2.9-degree average rise in 241 of 245 major U.S. cities analyzed.