San Diego weather in September
September in San Diego: warm, dry, with very humid — an excellent time to visit.
#3 of 12 months in San Diego · #103 of 604 destinations to visit in September · comfort 89/100 (tier A)
Updated June 2026 · climate normals from ERA5 reanalysis
San Diego climate normals — September
| Daytime high | 26°C / 79°F | 🌤 warm |
|---|---|---|
| Nighttime low | 19°C / 66°F | |
| Feels like (high) | 28°C / 82°F | |
| Rainfall | 9 mm / 0.4 in | ☀️ dry |
| Rainy days | 2 days | |
| Humidity | 78% | 💦 very humid |
| Dew point | 17°C / 63°F | |
| Sunshine | 11 h/day | |
| Daylight | 12.4 h | |
| Wind | 15 km/h / 9 mph | |
| Air quality (US AQI) | 53 | 🙂 moderate |
Monthly averages from ERA5 reanalysis. AQI is the mean US Air Quality Index for the month.
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San Diego in September — FAQ
- Is September a good time to visit San Diego?
- September in San Diego: warm, dry, with very humid — an excellent time to visit. It ranks #3 of 12 months for San Diego on SeasonMap's comfort score (89/100).
- What is the weather like in San Diego in September?
- In September, San Diego averages a daily high of 25.9°C and a low of 18.7°C, with about 9.1 mm of rain over roughly 1.8 rainy days.
- What is the air quality in San Diego in September?
- San Diego has a mean US Air Quality Index of about 53 in September.