May in Bilbao averages a daily high of 21°C with nights around 11.1°C. Expect roughly 13.1 wet days totalling 74.8mm. Generally workable, with some weather to plan around.
Across the year, the best time to visit Bilbao is May–October.
Based on BILBAO AEROPUERTO, SP (4.2km), 1995–2024. 30 years of May data.