Key West, FL weather in September
Expect hot, oppressively humid weather with rain on most days in Key West in September, with highs near 89°F and lows near 79°F. Rain falls on about 16 days. Pack rain gear.
- Normal high
- 89°F
- Normal low
- 79°F
- Wet days
- 16
- 7.2 in total
- Muggy days
- 30
- dew point 65°F+
How September changes from start to finish
| September 1 | September 30 | |
|---|---|---|
| Normal high | 90°F | 88°F |
| Normal low | 80°F | 79°F |
| Chance of a wet day | 52% | 49% |
| Sunrise / sunset | 7:08 am / 7:45 pm | 7:18 am / 7:15 pm |
| Daylight | 12.6 h | 11.9 h |
Chance of a wet day: average for the first and last 7 days of the month. Times are local clock time (Eastern Time).
A typical September day
- 6 am81°Fdew point 75°F
- 9 am85°Fdew point 75°F
- Noon87°Fdew point 76°F
- 3 pm86°Fdew point 75°F
- 6 pm84°Fdew point 75°F
- 9 pm83°Fdew point 75°F
NOAA hourly normals (local standard time) from Key West Intl Airport (2 mi away); average wind 9 mph; clear or few clouds in 62% of daytime hours, mostly cloudy or overcast in 22%.
What kind of days to expect
- Comfortable dayshigh 65-80°F and dew point under 60°F0 of 30
- Beach dayshigh 80-95°F, under 0.05 in of rain, afternoon wind under 15 mph17 of 30
- Hot dayshigh 90°F or more10 of 30
- Muggy daysdaily mean dew point 65°F or more30 of 30
- Wet daysat least 0.01 in of rain or melted snow16 of 30
- Notable rainat least 0.10 in10 of 30
- Freezing nightslow 32°F or below0 of 30
Average days per September, counted from daily records for each year 1991-2020.
Rain in September
Normal precipitation is 7.2 in; a dry September brings about 5.6 in and a wet one about 8.3 in (25th and 75th percentiles). About 4 days bring half an inch or more, and about 2 an inch or more.
How September varies from year to year
- Warmest September, 1991-20202007: average high 90°F
- Coolest September2008: average high 87°F
- Wettest September1994: 13.0 in
- Driest September2000: 4.0 in
- Highest reading95°F (September 20, 2018)
- Lowest reading71°F (September 29, 2001)
From the station's daily records with NOAA quality flags removed; most recent date shown when a reading repeats.
September compared with August and October
| August | September | October | |
|---|---|---|---|
| Normal high | 91°F | 89°F | 86°F |
| Normal low | 81°F | 79°F | 77°F |
| Wet days | 15 | 16 | 12 |
| Comfortable days | 0 | 0 | 1 |
| Daylight | 13.0 h | 12.3 h | 11.6 h |
Highs change by -2°F from August and -3°F into October.
Nearby alternatives in September
- Drier: Tampa, FL238 mi · high 90°F · 13 wet days
How Key West ranks in September
- Normal high71st warmest of 378 cities; 11th of 23 in Florida
- Wet days364th driest of 378
- Comfortable days328th most of 342
What to pack for Key West in September
- Light, breathable clothing – highs near 89°F and about 30 muggy days
- A rain jacket or umbrella – rain on about 16 days
- A swimsuit – about 17 beach days
Heating and cooling
September has 0 heating degree days and 573 cooling degree days (base 65°F), 11% of the year's total heating and cooling demand.
Questions
How hot is Key West in September?
The normal high is 89°F and the normal low is 79°F. From 1991 to 2020 the hottest September reading was 95°F (most recently on September 20, 2018).
Does it rain a lot in Key West in September?
About 16 days in September have at least 0.01 in of precipitation, and the normal total is 7.2 in. The wettest September in 1991-2020 was in 1994 (13.0 in); the driest was in 2000 (4.0 in).
Is September a good time to visit Key West?
September ranks 11th of 12 months on our comfort score for Key West (38 out of 100). It has almost no comfortable days and about 10 days at 90°F or hotter. The best months are January, February and March.
Where the numbers come from
- Temperature, rain, frost dates, humidity and wind by hour and cloud cover: Key West Intl Airport (USW00012836), 1.9 mi E of the city center, 4 ft . NOAA normals and daily records, 1991-2020.
- Daily humidity and wind: Key West International Airport (722010-12836), 1.7 mi E of the city center, 1 ft . Hourly observations, 1991-2020.
- Not available for this location: snowfall and snow depth (no station close enough or similar enough in elevation).