The Florida Keys run 200 km from Key Largo to Key West. Sheltered by the world's third-largest barrier reef, water sits between 24°C in winter and 30°C in summer — making this the only US coastline that stays comfortable for swimming all 12 months.
Florida Keys
Year-round swimmable water along the US's southernmost reef chain.
Sea
Atlantic Ocean / Gulf
Avg sea temp now
29.8°C
Best months
Year-round (calmest April – June)
Best time to swim in Florida Keys
The sea in Florida Keys peaks in July, when the water averages around 30°C.
The main swimming season runs from January – December, when surface temperatures stay comfortable for extended sessions.
On average, 12 months a year sit above 20°C — the threshold most swimmers describe as pleasant without a wetsuit.
The coldest month is typically January at around 23°C, when cold-water swimmers dominate the coast.
Florida Keys sea temperature history
Long-term climatology for Florida Keys shows an annual mean sea temperature of 27°C, ranging from 23°C in winter to 30°C at the summer peak.
The seasonal swing is roughly 7°C between the coldest and warmest month — a useful yardstick when comparing years or checking whether the current sea is running above or below average.
Recent decades have trended slightly warmer at Florida Keys, in line with regional sea-surface temperature records for the wider basin.
Monthly averages below are drawn from multi-decadal climatology and are updated as new observations arrive.
Jan
23°C
Feb
23°C
Mar
24°C
Apr
26°C
May
28°C
Jun
29°C
Jul
30°C
Aug
30°C
Sep
30°C
Oct
29°C
Nov
26°C
Dec
24°C
Values are area averages; individual beaches vary by exposure and depth.
Florida Keys sea temperature: frequently asked questions
What is the warmest month to swim in Florida Keys?
July is the warmest month in Florida Keys, when the sea averages about 30°C. Late-season warmth often persists a few weeks after peak.
When is the sea coldest in Florida Keys?
The coldest month in Florida Keys is typically January, when the water averages around 23°C. Cold-water swimmers and surfers dominate this period.
When can you swim in Florida Keys without a wetsuit?
The main swimming season in Florida Keys runs from January – December — about 12 months a year when the sea sits above 20°C, the level most swimmers describe as pleasant without a wetsuit.
Do I need a wetsuit in Florida Keys?
Florida Keys stays warm year-round, so most swimmers never need a wetsuit — a rash guard is usually enough for sun and wildlife protection.
What is the average sea temperature in Florida Keys?
The long-term annual mean sea temperature in Florida Keys is about 27°C, based on multi-decadal climatology of the surrounding waters.
How do I check the current sea temperature in Florida Keys?
The live reading at the top of this page shows the current sea temperature in Florida Keys, updated hourly from marine buoy and satellite data. The 7-day forecast covers water, air, waves, wind and UV for the week ahead.
Beaches in the Florida Keys
Ranked by current live sea temperature.
- 1Fort Zachary TaylorKey West, United States30.5°C
- 2Bahia HondaBig Pine Key, United States29.9°C
- 3Sombrero BeachMarathon, United States29.6°C
- 4Smathers BeachKey West, United States29.6°C
- 5Higgs BeachKey West, United States29.4°C
Swimming in the Florida Keys — FAQ
How warm is the sea in the Florida Keys in September?
The Atlantic Ocean / Gulf off the Florida Keys averages about 30.0°C in September, based on long-term monthly averages for this coast.
When is the best time to swim in the Florida Keys?
The Florida Keys is warmest in July (around 30.0°C) and coldest in January (around 23.0°C). There are typically 12 months a year when the water sits above 22°C.
What is the average yearly sea temperature in the Florida Keys?
Across all twelve months, the sea in the Florida Keys averages about 26.8°C.
Do you need a wetsuit to swim in the Florida Keys?
In peak season (around July, ~30.0°C) most swimmers are comfortable without a wetsuit. Outside summer, when the water drops toward 23.0°C, a 3/2mm to 5/4mm wetsuit is recommended.