September in Siegen averages a daily high of 19.7°C with nights around 7.9°C. Expect roughly 11.6 wet days totalling 62.6mm. Comfortable conditions for being outdoors all day.
Across the year, the best time to visit Siegen is May–September.
Based on DILLENBURG, GM (23.1km), 1995–2024. 27 years of September data.