September in Donostia / San Sebastián averages a daily high of 21.4°C with nights around 15°C. Expect roughly 12.4 wet days totalling 113.5mm. Comfortable conditions for being outdoors all day.
Across the year, the best time to visit Donostia / San Sebastián is June–October.
Based on SAN SEBASTIAN IGUELDO, SP (5.2km), 1995–2024. 30 years of September data.