May in Siegen averages a daily high of 19.1°C with nights around 6.4°C. Expect roughly 12.6 wet days totalling 64.9mm. Generally workable, with some weather to plan around.
Across the year, the best time to visit Siegen is May–September.
Based on DILLENBURG, GM (23.1km), 1995–2024. 28 years of May data.