May in Santander averages a daily high of 17.8°C with nights around 12.3°C. Expect roughly 12.3 wet days totalling 66.5mm. Generally workable, with some weather to plan around.
Across the year, the best time to visit Santander is June–October.
Based on SANTANDER CMT, SP (2.9km), 1995–2024. 29 years of May data.