September in Groningen averages a daily high of 19.4°C with nights around 9.5°C. Expect roughly 13.3 wet days totalling 74.5mm. Generally workable, with some weather to plan around.
Across the year, the best time to visit Groningen is May–September.
Based on EELDE, NL (10.7km), 1995–2024. 30 years of September data.