San Francisco weather by month
San Francisco runs from about 11°C in December to 17°C in October, with February the wettest month at 170 mm.
warmest month
October
17°C
coolest month
December
11°C
wettest month
February
170 mm
worst air month
December
19 µg/m³
The whole year, month by month.
| Month | Avg temp | Rain | Sun | PM2.5 |
|---|---|---|---|---|
| January | 11°C | 154 mm | 191 h | 17 |
| February | 11°C | 170 mm | 223 h | 14 |
| March | 12°C | 126 mm | 290 h | 15 |
| April | 13°C | 28 mm | 348 h | 11 |
| May | 14°C | 21 mm | 401 h | 9 |
| June | 16°C | 0 mm | 414 h | 10 |
| July | 16°C | 0 mm | 400 h | 9 |
| August | 16°C | 2 mm | 368 h | 10 |
| September | 16°C | 3 mm | 325 h | 13 |
| October | 17°C | 7 mm | 307 h | 13 |
| November | 13°C | 146 mm | 224 h | 17 |
| December | 11°C | 142 mm | 198 h | 19 |
About 3,689 hours of sun a year. Roughly 80 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.