Key West weather in September
Temperature, sea and sunshine in September: long-term averages from 30 years of weather data, not a forecast.
Holiday weather in September
Good
Best time to visit: March – July, November
What is the weather like in Key West in September?
In September, Key West is hot: daytime highs average 29 °C, and even at night it stays warm at around 27 °C. The sea averages 29.7 °C – almost as warm as a bath. The sun shines for around 7 hours a day. It rains often – on about 17 days, adding up to 134 mm. The air is often humid and muggy. All in all, September is a good month for a holiday in Key West.
September compared
How the weather changes from August to October. Tap a month to open it.
| AugustAug | SeptemberSep | OctoberOct | |
|---|---|---|---|
| Score | 81 | 75 | 81 |
| Day | 29° | 29° | 27° |
| Night | 28° | 27° | 26° |
| Sea | 30° | 30° | 28° |
| Sun | 8 h | 7 h | 7 h |
| Rain days | 16 | 17 | 12 |
More details for September
- Daylight
- 12 h 20 min07:13 – 19:32
- UV index
- 10 · very highclear sky, noon (estimate)All months
- Muggy days
- 30 daysdew point 18 °C or more
- Wind
- 24 km/haverage daily peak
- Cloud cover
- 62 %on average
- Hot days
- 0 days30 °C or more
- Time zone
- UTC−4America/New_York
How the score comes together
- Temperatureweight 35 %100 %
- Seaweight 25 %100 %
- Sunshineweight 20 %70 %
- Few rainy daysweight 20 %6 %
Each factor is rated from 0 to 100 % and weighted for the travel style “Sun, sea & sand”.
What to pack in September
- Swimwear
- Sunscreen
- Sunglasses & sun hat
- Light, breathable clothes
- Insect repellent
- Rain jacket or umbrella
Key West in September: quick answers
Is Key West hot in September?
Yes. In September, Key West is hot: daytime highs average 29 °C and nights stay around 27 °C.
Can you swim in Key West in September?
Yes. In September the sea averages 29.7 °C – almost as warm as a bath.
Does it rain much in Key West in September?
It rains often – on about 17 days, adding up to 134 mm.
Key West month by month
The whole year in Key WestAll destinations: USAFlorida weather in SeptemberWhere to go in SeptemberSea temperature in September
Climate averages 1996–2025, not a forecast. Data: Copernicus ERA5 / ERA5-Land via Open-Meteo.com (CC BY 4.0), NOAA OISST, WMO 1991–2020 (NOAA NCEI), GeoNames (CC BY 4.0)