Travel time: Year-round
San Sebastián (Donostia) is defined by its Temperate Oceanic Climate, characterized by mild winters, cool-to-warm summers, and abundant precipitation. Unlike the arid regions of southern Spain, this city is lush and green, receiving approximately 1,500 mm (59 inches) of rain annually. The proximity to the Cantabrian Sea stabilizes temperatures, preventing extreme heat and severe freezes, but also creates a landscape where the weather can change within minutes.
Spring is a season of transition where the city awakens. While temperatures gradually rise from 10°C to 20°C (50°F to 68°F), this is often the most unpredictable time of year. Dramatic Atlantic shifts can bring a sun-drenched morning followed by a sudden thunderstorm. This season is vital for the local cider houses (sagardotegis), as the damp, cool spring supports the region's apple harvests.
Summer is comfortably warm rather than scorching. Average highs reach 24°C–26°C (75°F–79°F), though occasional heat waves can push temperatures into the mid-30s°C (90s°F). This is the sunniest period, but rain is never entirely absent—cloudy intervals known as "grey mornings" are common, often clearing by mid-afternoon as the sea breeze kicks in. The Bay of Biscay reaches its peak swimming temperature of about 22°C (72°F) in August.
Early autumn (September) often feels like an extension of summer, known for stable, golden weather. However, as the season progresses into November, San Sebastián enters its wettest period. This is the heart of the "storm season," where powerful Atlantic swells draw surfers to Zurriola Beach. Temperatures decline from 20°C (68°F) in September to 12°C (54°F) by late November.
Winter is mild but damp and breezy. Frost is rare and snow at sea level is an event people talk about for decades (the last major snowfall was in 2018). Daytime temperatures usually hover around 8°C–12°C (46°F–54°F). When the Southerly Winds blow down from the mountains, they create a "foehn effect," occasionally spiking temperatures to a spring-like 20°C (68°F) even in January.
The topography of San Sebastián creates distinct weather zones. The Mount Igueldo meteorological station often records higher winds and cooler temperatures than the sheltered city center or the protected La Concha Bay. Neighborhoods located further inland and away from the coast can experience significantly warmer temperatures during summer afternoons, as they lack the immediate cooling effect of the sea air.
Historically, San Sebastián's climate made it the summer capital for Spanish royalty seeking refuge from the heat of Madrid. The locals, known as Donostiarras, have an almost defiant relationship with the rain. They are famous for their "all-weather" socializing; the pintxo crawls through the Old Town continue regardless of the forecast. A local proverb says, "Eguerdiko euria, egun guztiko euria" (Rain at midday, rain all day), reflecting a culture that has learned to read the sky as accurately as any instrument.