Key West weather in September
September in Key West: sweltering, rainy, with clean air — an excellent time to visit.
#10 of 12 months in Key West · #304 of 604 destinations to visit in September · comfort 80/100 (tier A)
Updated June 2026 · climate normals from ERA5 reanalysis
Key West climate normals — September
| Daytime high | 29°C / 84°F | 🔥 sweltering |
|---|---|---|
| Nighttime low | 27°C / 81°F | |
| Feels like (high) | 34°C / 93°F | |
| Rainfall | 140 mm / 5.5 in | 🌧 rainy |
| Rainy days | 16 days | |
| Humidity | 77% | 💦 very humid |
| Dew point | 24°C / 75°F | |
| Sunshine | 10.5 h/day | |
| Daylight | 12.3 h | |
| Wind | 23 km/h / 14 mph | |
| Air quality (US AQI) | 35 | 🍃 good |
Monthly averages from ERA5 reanalysis. AQI is the mean US Air Quality Index for the month.
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Key West in September — FAQ
- Is September a good time to visit Key West?
- September in Key West: sweltering, rainy, with clean air — an excellent time to visit. It ranks #10 of 12 months for Key West on SeasonMap's comfort score (80/100).
- What is the weather like in Key West in September?
- In September, Key West averages a daily high of 29°C and a low of 27.3°C, with about 140.2 mm of rain over roughly 16.2 rainy days.
- What is the air quality in Key West in September?
- Key West has a mean US Air Quality Index of about 35 in September.