When to visit
The summer months of July and August are the best times to visit northern Spain. Cities near the Atlantic like Santiago de Compostela, Oviedo, Santander, and San Sebastian experience their best weather and least amount of rainfall during these months.
If you’re looking just for a city break in northern Spain, you can pretty much visit any time of year. If you prefer outdoor activities however, then spring, summer or autumn are probably the best time to head there, but you may run the risk of encountering the rainy season, especially in the spring.