Illinois is enjoying a stretch of mild fall weather right now, but we all know how this goes: one day you’re sipping iced coffee, the next you’re scraping frost off your windshield with a rewards card because you forgot the scraper. NOAA Outlook: Don’t Pack Away the Shorts Just YetCanva Canva loading...Get our free mobile appNOAA’s seasonal outlook has Illinois leaning warmer than average through October, November, and December. But don’t get too cozy, Illinois weather is like that friend who says they’re “five minutes away” when they haven’t even left the house yet. First Frost: Rockford and BeyondCanva Canva loading... For northern Illinois, including Rockford, the average date is around October 12–13.