September weather in Key West, FL
The average temperature in Key West in September is 82.7°F (77.0°F–88.3°F). Average precipitation: 8.24 inches.
September is a fall month in Key West, and is warmer than the annual average of 77.4°F. Daily temperatures swing about 11.3°F between overnight low and afternoon high. Expect about 16 days with precipitation. Daylight averages about 12h 8m. For travel, September is a wet month.
Avg High
88.3°F
Avg Low
77.0°F
Precipitation
8.24 in
Daylight
12h 8m
September records in Key West
| Date | Record High | Record Low | Record Precip |
|---|---|---|---|
| September 1 | 91.9°F (2017) | 75.9°F (2018) | 0.66 in (2025) |
| September 2 | 93.0°F (2020) | 75.9°F (2014) | 0.97 in (2025) |
| September 3 | 91.9°F (2020) | 75.0°F (2013) | 1.33 in (2013) |
| September 4 | 93.0°F (2020) | 73.9°F (2025) | 1.85 in (2025) |
| September 5 | 93.0°F (2020) | 77.0°F (2020) | 0.06 in (2022) |
| September 6 | 91.0°F (2017) | 75.0°F (2016) | 1.27 in (2016) |
| September 7 | 93.0°F (2017) | 73.9°F (2013) | 1.68 in (2022) |
| September 8 | 91.9°F (2024) | 73.0°F (2022) | 0.54 in (2018) |
| September 9 | 93.0°F (2015) | 73.0°F (2014) | 2.67 in (2017) |
| September 10 | 91.9°F (2024) | 75.9°F (2014) | 2.77 in (2017) |
| September 11 | 91.9°F (2023) | 75.0°F (2014) | 0.32 in (2016) |
| September 12 | 91.0°F (2012) | 73.9°F (2014) | 11.36 in (2020) |
| September 13 | 91.0°F (2015) | 72.0°F (2014) | 1.01 in (2014) |
| September 14 | 91.9°F (2015) | 73.0°F (2014) | 0.65 in (2020) |
| September 15 | 91.9°F (2024) | 72.0°F (2013) | 1.36 in (2013) |
| September 16 | 91.9°F (2024) | 73.9°F (2013) | 0.89 in (2022) |
| September 17 | 91.0°F (2018) | 73.0°F (2012) | 1.55 in (2015) |
| September 18 | 91.0°F (2018) | 73.9°F (2024) | 1.05 in (2025) |
| September 19 | 91.0°F (2023) | 73.0°F (2023) | 0.72 in (2023) |
| September 20 | 90.0°F (2019) | 73.0°F (2012) | 0.58 in (2012) |
| September 21 | 90.0°F (2016) | 71.1°F (2023) | 3.49 in (2023) |
| September 22 | 90.0°F (2018) | 73.0°F (2023) | 0.30 in (2012) |
| September 23 | 91.9°F (2024) | 72.0°F (2014) | 1.62 in (2014) |
| September 24 | 91.0°F (2024) | 70.0°F (2023) | 2.25 in (2023) |
| September 25 | 90.0°F (2017) | 73.9°F (2019) | 0.44 in (2024) |
| September 26 | 90.0°F (2018) | 72.0°F (2019) | 1.65 in (2016) |
| September 27 | 91.0°F (2018) | 73.0°F (2016) | 3.90 in (2022) |
| September 28 | 91.0°F (2018) | 73.0°F (2013) | 2.02 in (2017) |
| September 29 | 90.0°F (2024) | 73.9°F (2013) | 0.85 in (2020) |
| September 30 | 91.0°F (2018) | 75.0°F (2016) | 0.25 in (2017) |