May in Sundsvall averages a daily high of 13°C with nights around 2.6°C. Expect roughly 9.9 wet days totalling 41.7mm. Generally workable, with some weather to plan around.
Across the year, the best time to visit Sundsvall is June–August.
Based on SIDSJO, SW (1.5km), 1995–2024. 12 years of May data.