September in Köln averages a daily high of 20.9°C with nights around 12.2°C. Expect roughly 11.9 wet days totalling 63.5mm. Comfortable conditions for being outdoors all day.
Across the year, the best time to visit Köln is May–September.
Based on KOLN STAMMHEIM, GM (6.7km), 1995–2024. 28 years of September data.