Key West weather in September

September in Key West: sweltering, soaked, with clean air — fine if you can take 13 rainy days.

Updated September 2026 · climate normals from ERA5 reanalysis

Key West🇺🇸 United States · Florida · Beach76
  1. 84Jan
  2. 89Feb
  3. 91Mar
  4. 90Apr
  5. 85May
  6. 82Jun
  7. 80Jul
  8. 78Aug
  9. 76Sep
  10. 81Oct
  11. 86Nov
  12. 83Dec

#12 of 12 months in Key West · #824 of 1413 destinations to visit in September · comfort 76/100 (tier B)

Days
32°C
Nights
26°C
Wet days
13
Sun
10.3 h
Humidity
79%
Daylight
12 h
Key West, United States
Photo: Arian Fernandez · Pexels

Traveller notes on Key West in September

Forum posters call September hot, humid and rainy, sitting right at the peak of hurricane season (which runs June-November, peaking late August into late September) - but they're consistent that actual disruption is rare. One repeat visitor of twenty consecutive Septembers reported being foiled by a hurricane only twice. The standard advice is simply to buy trip insurance and follow evacuation guidance if a storm does approach, not to avoid the month outright. The clear payoff for the hurricane-season gamble: genuine off-season pricing and noticeably lighter weekday crowds compared to the winter high season.
Tripadvisor community · September · 1 month ago · Read more on Tripadvisor ↗

Other months in Key West

Regulars are consistent this counts as genuinely pleasant overall, warm and sunny with little rain chance the norm, though several cold fronts each winter bring a handful of windy, noticeably chillier days, temperatures dropping 10-15 degrees below the run of the month. Our row backs that mild, still-dry read, 23.9C over 17.9C nights, with 46.9mm of rain across 5.2 days and a real 30.9 kph wind. Regulars are consistent this is high season here, prices climbing accordingly, jeans and a light sweater the standard packing advice for evenings and any cold-front days rather than a full coat. The sea sits at a swimmable 24.6C despite the water reading cooler than the air on paper. The record: humidity 77 percent, 9 hours of sun and AQI 45.
ColdFrontsBringAFewChillyWindyDays · January · 1 month ago · Read more on Tripadvisor ↗
Regulars call this a transitional month rather than a settled one - awesome, un-oppressive weather in some years, hot and humid in others, with the one consistent change being winter's wind finally easing off, which makes it a favoured month for getting out on the water. Our row leans toward the warmer read, 30.2C reading as 34C at 77.1 percent humidity, over 24.1C nights, with 103.6mm of rain across 6.9 days. Regulars are specific about the calendar that follows: real humidity builds from late May, June brings the heat and the start of hurricane season in earnest, so May is the last easy month before both arrive. The sea stays calm and warm at 28.6C, good for fishing and snorkelling either way. The record: 11.9 hours of sun, a 25.7 kph wind and AQI 44.
WindsDieDownBeforeTheHeatArrives · May · 1 month ago · Read more on Tripadvisor ↗
Key West-forum threads on November weather call it, along with October, one of the genuinely nice stretches of the year - warm days, cool nights, humidity down from summer's peak, closer in feel to spring than to the hurricane-season months just before it. Showers do still happen, but posters say it's rare for one to be more than something passing through rather than a washed-out day, and some stretches go by without a cloud in sight. The end of the month can turn unpredictable - a late-season storm or a couple of chillier days are possible - but the average still comes out ahead of what preceded it. High-season lodging rates don't kick in until mid-December, making early November good value too, alongside a couple of specific events in the first half of the month. The record: 27.3C days feeling like 29C, 21.9C nights, 68mm across 4.9 days, a 27.4C sea, 76 percent humidity, wind averaging over 29 km/h and 9.5 hours of sun.
DuvalStreetNovemberRegular · November · 1 month ago · Read more on Tripadvisor ↗
February in Key West is sunny and mostly dry - our row gives 41.4mm across 3.7 days - with an average high near 76F and a low near 66F, and most visitors getting 70s-to-80s days and cool nights. The word regulars repeat is windy. Our row's 28.6 kph is the strongest wind of the Key West year, and the consequences they list are the water ones: it is not a great month for water activities, and the wind is enough to make the ferry a poor bet. A cold front can also drop a couple of days into low-60s highs and low-50s nights, which is why the packing advice is shorts plus one sweatshirt. This is also peak season. The record: 26C days, 19.9C nights, 10.1 hours of sun and a 25.3C sea.
WindyEnoughToSkipTheFerry · February · 1 month ago · Read more on Tripadvisor ↗

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Key West climate normals — September

Daytime high32°C / 89°F🔥 sweltering
Nighttime low26°C / 78°F
Feels like (high)37°C / 99°F
Sea temperature31°C / 88°F♨️ bath-warm
Rainfall195 mm / 7.7 in⛈ soaked
Rainy days13 days
Humidity79%💦 very humid
Dew point24°C / 76°F
Sunshine10.3 h/day
Daylight12.3 h
Wind23 km/h / 14 mph
Air quality (US AQI)35🍃 good

Monthly averages from ERA5 reanalysis. AQI is the mean US Air Quality Index for the month.

Crowds in Key West in September

How busy the place itself is — school and mass holidays, the months an editor tagged, and how sought-after the weather makes them. Never part of the comfort score.

BusySummer break in United States(estimated)

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Peak crowdsBusyShoulder seasonQuiet

Best months for Key West's weather

Ranked by this destination's own climate comfort score across the year — a different thing from how busy it gets (see Crowds above).

Fair weatherKey West's weather doesn't swing hard through the year — comfort stays fairly steady in every month.

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What's on in Key West in September

Recurring seasonal events, natural spectacles, closures and holidays — curated and sourced.

  • Hazard

    Hurricane season

    1 Jun – 30 Nov

    The island is four feet above the sea at the highest and reached by one road with forty-two bridges, so evacuation is ordered early and the Overseas Highway closes long before landfall. September is the peak. Source ↗

What's on around the world in September →

Nearby, and something's on

Within 300 km of Key West — a day trip or a short hop — with something on this month. Never part of the comfort score.

Where is Key West?

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Key West in September — FAQ

Is September a good time to visit Key West?
September in Key West: sweltering, soaked, with clean air — fine if you can take 13 rainy days. It ranks #12 of 12 months for Key West on SeasonMap's comfort score (76/100).
What is the weather like in Key West in September?
In September, Key West averages a daily high of 31.5°C and a low of 25.5°C, with about 195.3 mm of rain over roughly 12.7 rainy days.
What is the air quality in Key West in September?
Key West has a mean US Air Quality Index of about 35 in September.

Within 300 km: Naples, Florida's Sea turtle nesting on 1 May – 31 Oct, and Miami's Sea turtle nesting on 1 Mar – 31 Oct.