May in Biel/Bienne averages a daily high of 19.2°C with nights around 8.1°C. Expect roughly 13.8 wet days totalling 85.4mm. Generally workable, with some weather to plan around.
Across the year, the best time to visit Biel/Bienne is June–September.
Based on PAYERNE, SZ (42.1km), 1995–2024. 30 years of May data.