May in Vaasa averages a daily high of 14°C with nights around 3.6°C. Expect roughly 12 wet days totalling 36.4mm. Generally workable, with some weather to plan around.
Across the year, the best time to visit Vaasa is July–August.
Based on VAASA VAASAN LENTOASEMA, FI (9.8km), 1995–2024. 17 years of May data.