Key West Weather in September
Thinking of visiting Key West in September? Expect very high temperatures reaching 32°C (90°F) during the day, dropping to 26°C (79°F) at night, and be prepared for the wettest month of the year.
Rainfall in Key West in September
Expect the heaviest rain of the year this month, often arriving in intense bursts. A poncho is essential for keeping dry. On average, there are about 23 days with rain during this month, averaging 163 mm (6.4 in). Rain falls regularly this month and can be quite heavy when it does. Showers can be substantial, so waterproof gear is a good idea.
Temperature in Key West in September
If you're visiting Key West in September, expect highs of 32°C (90°F) and overnight lows around 26°C (79°F). Sunshine and humidity can make it feel even warmer than the raw temperature suggests. At 26°C (79°F) overnight, the heat doesn't let up much after dark. If you're staying somewhere without air conditioning, a cold shower before bed and keeping the air moving can help.
Sunshine in Key West in September
The city usually sees around 271 hours of sunlight, indicating many sunny days — a great month for sightseeing.
Average water temperature in September
The water is 30°C (86°F) — very warm by most standards. Comfortable to swim in, but not particularly refreshing if you're looking to cool off.September in Key West has its charm, but if you're looking for destinations with pleasant temperatures and sunny skies, our weather planner can help you explore other options in the world.
Check the conditions for any month of the year.
For a detailed overview over the year and the best time to visit the United States of America, check out our Key West's climate page.
Key West Temperature in September
Min Temperature
26°C (79°F)
Max Temperature
32°C (90°F)
Water Temperature
30°C (86°F)
Chance of Rain
76%
Precipitation
163 mm (6.4 in)
Rainy days
23 days
Humidity
75%
Sunshine
271 hours
Percentage Sunshine
73%
Daily Historical Temperatures
50-year average (1976-2025)
Based on our historical records, temperatures in Key West typically stay consistent throughout September, with daily highs averaging around 32°C (90°F). Nights are warm, with lows around 26°C (79°F).
Average temperatures in September
Daily Historical Precipitation
50-year average (1976-2025)
Average daily rainfall for each day of the month based on long-term records.
Average precipitation in September
Historical weather for Key West in September
Browse day-by-day weather records for Key West spanning 51 years. Select any month and year to see actual temperatures, rainfall, and conditions recorded on each day.
Key West historical weather extremes in September
According to our 49 years of weather records for Key West, the following extremes were recorded between 1976 and 2025.
- On September 5, 2024, temperatures climbed to 35°C (95°F), marking the warmest September day on record.
- Key West experienced its chilliest September day on September 29, 1994, reaching only 26°C (79°F).
- Key West registered its coldest September night on September 17, 1985, with temperatures dropping to 21°C (70°F).
Best Places in the United States of America in September
Find out more about the weather in the United States of America and which places have the best travel conditions in this month. See all of the United States of America in September →
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What to Wear in Key West in September
Warm temperatures in September make for comfortable sightseeing weather. Pack breathable fabrics like cotton shirts, knee-length shorts or skirts, and comfortable walking shoes. A thin long sleeve for indoor spaces is handy. Heavy rain is guaranteed, please bring a good poncho and waterproof everything! The water temperature sits at about 30°C (86°F), making it perfect for swimming and water activities. Don't forget to pack your favorite swimwear and perhaps some snorkel gear. You'll definitely want to pack sunglasses and sunscreen. There will be plenty of bright sunshine this month.What To Do in Key West in September
We rated the following activities from 1 (least suitable) to 10 (best) to do.
Check the conditions for any month of the year.
For a detailed overview over the year and the best time to visit the United States of America, check out our Key West's climate page.
Temperature Rainfall Sunshine Humidity Water Temp
See the full Key West climate overview or explore weather in the United States of America.
