May in Leiden averages a daily high of 18°C with nights around 8.2°C. Expect roughly 11.9 wet days totalling 61.5mm. Generally workable, with some weather to plan around.
Across the year, the best time to visit Leiden is May–September.
Based on ROTTERDAM, NL (22.2km), 1995–2024. 30 years of May data.