May in Köln averages a daily high of 20°C with nights around 10.4°C. Expect roughly 13 wet days totalling 65.4mm. Generally workable, with some weather to plan around.
Across the year, the best time to visit Köln is May–September.
Based on KOLN STAMMHEIM, GM (6.7km), 1995–2024. 28 years of May data.