Best Time to Visit San Sebastián 2026: Seasonal Planning Guide Key Takeaways Peak Season Excellence (July-August 2026): Warmest temperatures 19-24°C, minimal rainfall 85-90mm monthly, premium festival lineup including Jazzaldia and Semana Grande, but accommodation costs €300-450 per night. Optimal Value Window (May-June & September 2026): Pleasant temperatures 16-21°C, moderate crowds, hotel rates […]