Month by month
| Month | Afternoon | Sea | Rain | Verdict |
|---|---|---|---|---|
| January | 13.7 °C | 12.1 °C | 10 days | Possible, with trade-offs |
| February | 14.9 °C | 12.2 °C | 8 days | Possible, with trade-offs |
| March | 15 °C | 12.2 °C | 10 days | Possible, with trade-offs |
| April | 16.1 °C | 11.9 °C | 5 days | Possible, with trade-offs |
| May | 17 °C | 12.1 °C | 2 days | Possible, with trade-offs |
| June | 19.3 °C | 13.1 °C | 0 day | Pleasant — a good time to go |
| July | 19.3 °C | 14.1 °C | 0 day | Pleasant — a good time to go |
| August | 20.1 °C | 15.1 °C | 0 day | Pleasant — a good time to go |
| September | 21.3 °C | 15.1 °C | 1 day | Pleasant — a good time to go |
| October | 20.6 °C | 14.4 °C | 3 days | Pleasant — a good time to go |
| November | 16.5 °C | 13.2 °C | 7 days | Possible, with trade-offs |
| December | 13.5 °C | 12.2 °C | 10 days | Possible, with trade-offs |
Before you go
Three things to check once you have picked your dates.
Entry
Entry rules depend on your nationality and change often. Check them before booking.
Safety
No specific restrictions
Usual precautions apply.
Official advice updated 18 August 2026
Health
Recommended vaccinations, water quality, mosquitoes: advice depends on the country and the season. Some vaccines need time before departure.
Beau Fixe is not a safety or health authority. These notes summarise public advisories and link to their source; only the competent authorities are authoritative. Alert levels: Foreign, Commonwealth & Development Office (gov.uk), Open Government Licence v3.0.
FAQ
Can you swim in San Francisco in September?
The sea averages 15.1°C in September — too cold for most swimmers.
How hot is San Francisco in September?
Expect 21.3°C in the afternoon and 14.4°C at night, averaged over the last 10 years.
Does it rain a lot in San Francisco in September?
Around 1 days with rain (≥ 1 mm) in the month — 3% of days.