September in Berwyn averages a daily high of 25°C with nights around 15.3°C. Expect roughly 8.8 wet days totalling 65.9mm. Comfortable conditions for being outdoors all day.
Across the year, the best time to visit Berwyn is May–June.
Based on CHICAGO MIDWAY AIRPORT, IL US (8km), 1995–2024. 28 years of September data.