September in Hamm averages a daily high of 20.6°C with nights around 10.4°C. Expect roughly 11.4 wet days totalling 51.4mm. Comfortable conditions for being outdoors all day.
Across the year, the best time to visit Hamm is May–September.
Based on WERL, GM (12.3km), 1995–2024. 20 years of September data.