September in Aachen averages a daily high of 18.6°C with nights around 10.1°C. Expect roughly 11.7 wet days totalling 61.2mm. Generally workable, with some weather to plan around.
Across the year, the best time to visit Aachen is June–September.
Based on NIDEGGEN SCHMIDT, GM (26.5km), 1995–2024. 30 years of September data.