What the averages say
The mean annual temperature is 13.8 °C. The warmest month is August, averaging 19.9 °C with highs around 22.9 °C; the coldest is January, averaging 8.6 °C with lows of 6.1 °C. The 17 degrees between the mean high of August and the mean low of January are the real measure of how continental this climate is.
Heat, cold and extremes
On average, 6 days a year reach 30 °C or more and 6 bring frost. Neither heat nor cold dominates the year. The highest reading in the series is 39.0 °C, set in July, and the lowest -5.6 °C, in December.
Rain, sun and wind
1566 mm fall each year over 191 days with measurable rain, an amount with a summer clearly drier than the rest of the year: November is the wettest month with 202 mm and July the driest with 92 mm. The sky is clear on 33 days a year. Mean wind speed is around 15 km/h and mean annual relative humidity 78 %.
Month by month
AEMET climate normals 1991-2020. Donostia / San Sebastián, Igeldo observatory, 5.0 km from the centre at 250 m above sea level.| Monthly mean | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
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| Mean temperature | 8.6 | 8.8 | 10.6 | 11.9 | 14.7 | 17.2 | 19.1 | 19.9 | 18.0 | 15.6 | 11.5 | 9.4 |
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| Mean high | 11.2 | 11.6 | 13.7 | 15.1 | 18.0 | 20.3 | 22.0 | 22.9 | 21.2 | 18.6 | 14.1 | 12.0 |
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| Mean low | 6.1 | 5.8 | 7.5 | 8.7 | 11.3 | 14.1 | 16.2 | 16.8 | 14.8 | 12.5 | 8.8 | 6.9 |
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| Rainfall (mm) | 151 | 124 | 119 | 126 | 122 | 96 | 92 | 109 | 117 | 155 | 202 | 153 |
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| Rain days | 16.4 | 13.3 | 14.2 | 16.7 | 17.3 | 16.4 | 16.7 | 16.1 | 14.7 | 16.5 | 16.7 | 16.4 |
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| Days ≥ 30 °C | 0.0 | 0.0 | 0.0 | 0.1 | 0.5 | 1.4 | 1.3 | 2.1 | 0.6 | 0.0 | 0.0 | 0.0 |
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| Frost days | 1.7 | 1.7 | 0.4 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.2 | 1.5 |
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Where this data comes from
These are the 1991-2020 climate normals published by AEMET, the Spanish state meteorological agency, for the Donostia / San Sebastián, Igeldo observatory — the nearest official station with a complete series to San Sebastian today. A normal is not a forecast: it describes a thirty-year average, and any given day can depart from it widely. For tomorrow, use the forecast at the top of this page.
