National Weather Service forecasts and ensemble model guidance indicate a high near 72–75°F for Chicago on September 29, driven by morning patchy fog clearing to mostly sunny skies, light southerly winds, and seasonal warmth about 5°F above normal. Trader consensus heavily favors the 76–77°F bin (57% implied probability) over lower ranges, reflecting expectations that inland sites or peak afternoon readings could edge higher amid variable lake-effect moderation and limited cloud cover. The 78–79°F outcome holds secondary support (26.5%) as models show minor upside potential before increasing clouds and showers arrive overnight. Resolution hinges on official maximum observations across Chicago reporting stations, with fresh model updates and real-time surface data likely to refine positioning before market close.