September in Haarlem averages a daily high of 19.6°C with nights around 11.3°C. Expect roughly 13.5 wet days totalling 82.2mm. Generally workable, with some weather to plan around.
Across the year, the best time to visit Haarlem is May–September.
Based on SCHIPHOL, NL (12.7km), 1995–2024. 30 years of September data.