San Francisco in September
Warm and clear
- Temperature
- 13–21°C
- Crowds
- Moderate–High
- Prices
- $$$
+The warmest, clearest weather.
–Conference weeks can be pricey.
September is San Francisco's real summer, with warm, clear days and less fog.
San Francisco vs San Diego in September
San Francisco and San Diego are close in September. San Francisco averages 13–21°C with moderate–high crowds; San Diego 19–25°C with moderate crowds.
By Daan · Last reviewed October 2026
San Francisco and San Diego
The verdict for September
- WeatherVery similar9/10 vs 9/10
- CrowdsSan Diego is quieterModerate–High vs Moderate
- PricesSan Diego is cheaper$$$ vs $$$
- OverallVery similar7/10 vs 7/10
San Diego in September
Summer without crowds
- Temperature
- 19–25°C
- Crowds
- Moderate
- Prices
- $$$
+Warm water, fewer people.
–Hot spells are possible inland.
September has summer weather without the summer crowds, once Labor Day passes.
Scores and crowd levels are my own judgement; temperatures are monthly averages. Higher scores are better: quieter, cheaper and more pleasant.
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