September in Wheaton averages a daily high of 24.7°C with nights around 12°C. Expect roughly 9.5 wet days totalling 74.5mm. Comfortable conditions for being outdoors all day.
Across the year, the best time to visit Wheaton is May–June.
Based on CHICAGO WEST CHICAGO DUPAGE AIRPORT, IL US (12.4km), 1995–2024. 28 years of September data.