Chicago, IL — Chicago tied with 1908 and 1960 for the second-warmest September on record, according to the National Weather Service (NWS). Average temperatures at O’Hare Airport hit 70.6°F, 4.3°F above normal. Rockford also experienced higher-than-usual temperatures, averaging 67.0°F, 2.6°F above normal.
According to the NWS, most of September’s warmth came from a stagnant air pattern and dry conditions. Chicago recorded just 1.32 inches of rain, 1.87 inches below average, while Rockford saw 2.05 inches, 1.57 inches below normal. The lack of rain, combined with dormant vegetation, likely enhanced the heating effects in urban areas.
Experts from NWS note that abnormally warm Lake Michigan waters contributed to higher temperatures. Dry ground also intensified heat, as it cools less effectively. Aurora Airport, located west of Chicago, saw even higher temperatures, reaching an average of 80.3°F.
Forecasters expect cooling trends heading into October, but September’s heat will be remembered for its near-record warmth and dry spell.
