Monday could be the warmest Oct. 27 in 74 years, but a cold front will drive temperatures down through the week and Halloween could see highs only in the 40s.
The high Monday is expected to be in the middle 70s, about 20 degrees above normal thanks to gusty southern winds. That would be the warmest Oct. 27 since it reached 79 in 1940, according to the Chicago Weather Center. Some areas could see 80 degrees or warmer.
Cooler air will arrive overnight, along with showers and some thunderstorms, according to the National Weather Service. The high Tuesday will be around 60, then drop to the lower 50s for Wednesday and Thursday.
The forecast for Friday, Halloween, is for highs in the 40s and lows in the lower 30s under cloudy skies, the weather service said.
The longer-range forecast is looking up, though, according to the Chicago Weather Center.
Both the six-to-10-day and the eight-to-14-day forecast from the Climate Prediction Center have above-average temperatures Nov. 1 through Nov. 9. The six-to-10-day forecast has much of the middle of the nation with above-average temperatures, while the eight-to-14-day forecast has almost the entire country with above-average temperatures.
A warmer-than-average November would be welcome since the first two months of fall have been below average. September saw an average temperature of 63.9 degrees, or 0.7 degrees below average. So far, October has seen an average temperature of 52.6 degree, 0.8 degrees below average.
The Chicago Tribune contributed to this report.