May in Heerlen averages a daily high of 18.9°C with nights around 8.7°C. Expect roughly 12.5 wet days totalling 62.8mm. Generally workable, with some weather to plan around.
Across the year, the best time to visit Heerlen is May–September.
Based on MAASTRICHT, NL (15.6km), 1995–2024. 30 years of May data.