San Sebastián weather by month
San Sebastián runs from about 10°C in December to 21°C in August, with December the wettest month at 246 mm.
warmest month
August
21°C
coolest month
December
10°C
wettest month
December
246 mm
worst air month
March
8 µg/m³
The whole year, month by month.
| Month | Avg temp | Rain | Sun | PM2.5 |
|---|---|---|---|---|
| January | 10°C | 114 mm | 175 h | 5 |
| February | 12°C | 216 mm | 159 h | 6 |
| March | 12°C | 162 mm | 252 h | 8 |
| April | 13°C | 88 mm | 274 h | 7 |
| May | 15°C | 148 mm | 313 h | 6 |
| June | 18°C | 133 mm | 279 h | 8 |
| July | 20°C | 72 mm | 318 h | 5 |
| August | 21°C | 82 mm | 311 h | 8 |
| September | 17°C | 216 mm | 273 h | 5 |
| October | 17°C | 225 mm | 211 h | 6 |
| November | 14°C | 99 mm | 212 h | 4 |
| December | 10°C | 246 mm | 173 h | 7 |
About 2,950 hours of sun a year. Roughly 181 rainy days a year.
These are long-run climate normals, not a forecast. A given year can sit well outside them. PM2.5 is a global model: near the coast it counts sea salt as fine particulate and reads high against ground stations, sometimes by a factor of two. Use the shape of the year, not the absolute number.
where these numbers come from
- · Temperature, rainfall and sunshine: ECMWF ERA5 reanalysis climate normals via Open-Meteo (CC BY 4.0), fetched once and stored.
- · PM2.5: Copernicus CAMS reanalysis, monthly means. Modelled, not station readings; near coasts CAMS counts sea salt as PM2.5 and reads high.
Last reviewed 2026-05-23. Full method, licences and the list of sources we rejected are on the methodology page.