San José weather in September
September in San José: warm, soaked, with clean air — fine if you can take 29 rainy days.
#7 of 12 months in San José · #732 of 897 destinations to visit in September · comfort 66/100 (tier C)
Updated June 2026 · climate normals from ERA5 reanalysis
Traveller notes on San José in September
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San José climate normals — September
| Daytime high | 25°C / 76°F | 🌤 warm |
|---|---|---|
| Nighttime low | 18°C / 65°F | |
| Rainfall | 390 mm / 15.3 in | ⛈ soaked |
| Rainy days | 29 days | |
| Humidity | 92% | 💦 very humid |
| Dew point | 19°C / 67°F | |
| Sunshine | 8.5 h/day | |
| Daylight | 12.2 h | |
| Wind | 6 km/h / 4 mph | |
| Air quality (US AQI) | 32 | 🍃 good |
Monthly averages from ERA5 reanalysis. AQI is the mean US Air Quality Index for the month.
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San José in September — FAQ
- Is September a good time to visit San José?
- September in San José: warm, soaked, with clean air — fine if you can take 29 rainy days. It ranks #7 of 12 months for San José on SeasonMap's comfort score (66/100).
- What is the weather like in San José in September?
- In September, San José averages a daily high of 24.6°C and a low of 18.3°C, with about 389.8 mm of rain over roughly 29 rainy days.
- What is the air quality in San José in September?
- San José has a mean US Air Quality Index of about 32 in September.