September weather in Key Biscayne, FL
The average temperature in Key Biscayne in September is 84.5°F (78.7°F–90.3°F). Average precipitation: 7.54 inches.
September is a fall month in Key Biscayne, and is warmer than the annual average of 78.7°F. Daily temperatures swing about 11.6°F between overnight low and afternoon high. Expect about 15 days with precipitation. Daylight averages about 12h 9m. For travel, September is a wet month.
Avg High
90.3°F
Avg Low
78.7°F
Precipitation
7.54 in
Daylight
12h 9m
September records in Key Biscayne
| Date | Record High | Record Low | Record Precip |
|---|---|---|---|
| September 1 | 93.0°F (2017) | 73.9°F (1999) | 2.25 in (2025) |
| September 2 | 93.9°F (2017) | 73.9°F (2023) | 0.74 in (2021) |
| September 3 | 93.0°F (2022) | 75.9°F (2023) | 2.21 in (2018) |
| September 4 | 91.9°F (2020) | 75.0°F (2002) | 1.60 in (2018) |
| September 5 | 93.9°F (2019) | 71.1°F (2002) | 1.93 in (2006) |
| September 6 | 93.0°F (2019) | 66.0°F (2002) | 3.21 in (2003) |
| September 7 | 93.0°F (2019) | 75.0°F (2005) | 2.40 in (1997) |
| September 8 | 93.0°F (2019) | 71.1°F (1999) | 3.20 in (1999) |
| September 9 | 93.9°F (2022) | 73.0°F (2007) | 1.38 in (2007) |
| September 10 | 95.0°F (2012) | 72.0°F (2001) | 3.44 in (2001) |
| September 11 | 95.0°F (2022) | 73.0°F (2005) | 1.99 in (2005) |
| September 12 | 93.9°F (2022) | 70.0°F (2002) | 3.23 in (2001) |
| September 13 | 93.0°F (2015) | 72.0°F (2001) | 2.75 in (2020) |
| September 14 | 93.9°F (2015) | 73.0°F (2005) | 1.27 in (2001) |
| September 15 | 93.0°F (2009) | 73.9°F (2001) | 1.53 in (2023) |
| September 16 | 93.9°F (2019) | 71.1°F (2001) | 3.97 in (1997) |
| September 17 | 93.9°F (2019) | 72.0°F (2001) | 1.13 in (1998) |
| September 18 | 91.9°F (2018) | 72.0°F (2000) | 1.75 in (1998) |
| September 19 | 91.9°F (2020) | 73.9°F (2004) | 0.82 in (1999) |
| September 20 | 93.9°F (2015) | 73.9°F (2004) | 0.97 in (2009) |
| September 21 | 93.9°F (2015) | 73.9°F (2004) | 1.10 in (1999) |
| September 22 | 93.0°F (2022) | 72.0°F (2001) | 1.02 in (2012) |
| September 23 | 93.0°F (2022) | 73.9°F (1999) | 2.49 in (2012) |
| September 24 | 93.0°F (2022) | 73.0°F (2002) | 2.99 in (2015) |
| September 25 | 91.0°F (2013) | 71.1°F (2019) | 1.24 in (2020) |
| September 26 | 91.9°F (2013) | 73.0°F (2003) | 1.43 in (2021) |
| September 27 | 93.0°F (2013) | 72.0°F (2007) | 2.50 in (2022) |
| September 28 | 91.9°F (2024) | 70.0°F (2001) | 3.16 in (2022) |
| September 29 | 93.0°F (2024) | 72.0°F (2001) | 4.76 in (2001) |
| September 30 | 91.9°F (2020) | 70.0°F (2022) | 3.19 in (2010) |