Key West sea temperature today: 31°C – beach water temperature, Key West, United States
Interactive map
United States · Florida Keys
Key West
Sea
31.3°C88.3°F
Air
–
UV
–
Bathtub
Above ⁦28°C⁩

Last updated ·

Today, September 13, the sea temperature at Key West is 31.3 °C (88 °F). That is 0.9 °C warmer than the usual 30.5 °C in September. Comfortable for swimming year-round.

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Climate · monthly averages

Sea temperature by month

5-year averages (2021–2025). Min/Max are typical daily lows and highs, not record extremes.

Warmest in August (30.8°C). Coldest in January (23.3°C). Comfortable for swimming year-round.

5-year averages (2021–2025). Min/Max are typical daily lows and highs, not record extremes.
MonthSea · MinSea · AvgSea · MaxAir · MinAir · AvgAir · Max
January22.4°C23.3°C24.1°C21.6°C21.7°C21.8°C
February22.6°C23.6°C24.7°C22.6°C22.8°C23.0°C
March24.3°C24.9°C25.5°C23.6°C23.8°C24.0°C
April25.5°C26.0°C26.7°C24.5°C24.8°C25.1°C
May27.6°C28.1°C28.7°C26.3°C26.7°C27.0°C
June28.8°C29.4°C29.9°C27.4°C27.7°C27.9°C
July29.6°C30.4°C31.3°C28.4°C28.7°C28.9°C
August30.3°C30.8°C31.4°C28.6°C28.9°C28.9°C
September30.1°C30.4°C30.7°C28.0°C28.3°C28.4°C
October28.1°C28.6°C28.9°C26.5°C26.8°C26.8°C
November26.0°C26.5°C27.1°C24.7°C24.9°C25.0°C
December23.9°C24.8°C25.3°C23.1°C23.3°C23.4°C

About Key West

Key West sits at the southern tip of the Florida Keys, last island on the Overseas Highway and southernmost city in the contiguous United States. Its calling card is the Southernmost Point Buoy, a painted concrete cone at South and Whitehead Streets announcing 90 miles to Cuba. Smathers Beach runs the longest strand of imported sand along the Atlantic shore, while Fort Zachary Taylor offers deeper, snorkel-friendly water inside the historic state park. The sea holds 29-31 °C84-88 °F from July through September, with Key West International airport 10 minutes away.

Frequently asked questions

Today, September 13, the sea at Key West is 31.3 °C (88 °F)88 °F (31.3 °C) – bathtub-warm. The usual September average is 30.5 °C87 °F.

No single number works for everyone, so the scale on this page is only a guide to how the water feels: below 13 °C55 °F icy, 13–18 °C55–64 °F cold, 18–23 °C64–73 °F refreshing, 23–28 °C73–82 °F pleasantly warm and above 28 °C82 °F like a bath. Right now the sea at Key West is 31.3 °C88 °F.

Yes – the sea at Key West (Florida Keys, United States) stays swimmable all year. January is the coolest month, averaging 23.3 °C74 °F – ideal for swimming for most people; the warmest is August at 30.8 °C87 °F.

In August, at 30.8 °C87 °F on average. The coolest month is January at 23.3 °C74 °F – still above the 18 °C64 °F swimming line, so there is no off-season for swimming.