Climate averages 1991–2020
San Francisco weather
in September.
A warm, very dry month: the warmest and the 3rd driest of the year. Meets the pleasant-weather rule
Long-term climate patterns, not a forecast for a particular trip.
September is a warm month in San Francisco: daytime highs average 22.7°C and nights cool to about 13.0°C. By daytime temperature it is the warmest month of the year.
Expect about 1.5 mm of rain on fewer than one day, which makes September a very dry month (the 3rd driest of the 12 months). Daylight, from sunrise to sunset, lasts about 12 h 28 min on an average September day.
The nearest other city in this atlas is Daly City (9 km away). In September its highs average 20.1°C, 2.6°C cooler than San Francisco, with 1.5 mm of rain.
Among the 498 cities listed in the United States, San Francisco ranks joint 419th of 498 for the warmest September highs and joint 6th of 498 for the driest September (rainfall, lowest first). The mean September high of those 498 cities is 26.9°C; San Francisco is 4.2°C cooler than that mean.
From September to October, average highs fall by 1.7°C to 21.0°C, and monthly rainfall rises from 1.5 mm to 24 mm.
The annual picture
September in context
Monthly rainfall
Average total · mmAverages from hourly ERA5 reanalysis data. Actual weather varies from year to year. How these numbers are calculated
Every month, side by side
San Francisco climate table
| Month | Average highHigh / low | Average low | Rainfall mm/month | Rain days ≥1 mm/day | Daylight hours/dayDaylight h/day |
|---|---|---|---|---|---|
| January | 13.6°C6.1°C | 6.1°C | 109 | 10.1 | 9.910 h |
| February | 14.6°C7.0°C | 7.0°C | 113 | 9.5 | 10.811 h |
| March | 15.7°C8.1°C | 8.1°C | 81 | 9.3 | 11.912 h |
| April | 17.0°C8.8°C | 8.8°C | 37 | 5.0 | 13.113 h |
| May | 18.8°C10.4°C | 10.4°C | 18 | 2.8 | 14.214 h |
| June | 21.0°C11.7°C | 11.7°C | 4.3 | 0.8 | 14.715 h |
| July | 21.5°C12.6°C | 12.6°C | 0.3 | 0.1 | 14.515 h |
| August | 22.1°C13.2°C | 13.2°C | 0.7 | 0.1 | 13.614 h |
| September, selected | 22.7°C13.0°C | 13.0°C | 1.5 | 0.4 | 12.512 h |
| October | 21.0°C11.8°C | 11.8°C | 24 | 3.1 | 11.311 h |
| November | 16.6°C8.7°C | 8.7°C | 56 | 6.1 | 10.210 h |
| December | 13.5°C6.3°C | 6.3°C | 108 | 10.1 | 9.610 h |
Rainfall is the average of the 30 separate monthly totals. A rain day is a local calendar day with at least 1 mm of precipitation. Daylight is the calculated sunrise-to-sunset length, not measured sunshine.
Compare places
September in nearby cities
- Daly City in SeptemberUnited States · 9 kmHigh 20.1°C · Low 12.6°C · 1.5 mm rain
- Oakland in SeptemberUnited States · 13 kmHigh 26.2°C · Low 13.8°C · 1.4 mm rain
- Berkeley in SeptemberUnited States · 17 kmHigh 26.2°C · Low 13.2°C · 1.4 mm rain
- San Mateo in SeptemberUnited States · 25 kmHigh 24.0°C · Low 14.2°C · 1.8 mm rain
- Hayward in SeptemberUnited States · 32 kmHigh 26.5°C · Low 14.3°C · 1.7 mm rain
- Redwood City in SeptemberUnited States · 36 kmHigh 24.6°C · Low 14.5°C · 1.8 mm rain
- San Ramon in SeptemberUnited States · 39 kmHigh 27.4°C · Low 14.1°C · 1.7 mm rain
- Vallejo in SeptemberUnited States · 39 kmHigh 28.2°C · Low 13.5°C · 1.8 mm rain
Read the numbers correctly
Climate, not a promise.
These patterns help compare months. They cannot tell you the weather on a specific day of your trip.
Sources, method and limitsHow these numbers are made (what the highs, lows and rain days mean, the sources and the model cell used for San Francisco) is explained once on the San Francisco year overview and on the Sources, method and limits page.
Daly City lies in the same rainfall cell, so its rainfall figures are identical to these; temperatures differ because they come from smaller 0.1° cells.