Key Largo water temperatures range from approximately 70°F (21°C) in the winter months to 86°F (30°C) at the peak of summer. The water is warm enough to snorkel or dive comfortably year-round – no wetsuit required for most of the year, though one makes a difference in winter.
Key Largo water temperature by month
| Month | Avg Water Temp (°F) | Avg Water Temp (°C) | Notes |
|---|---|---|---|
| January | 70-72°F | 21-22°C | Coolest month – 3mm wetsuit recommended |
| February | 70-72°F | 21-22°C | Still cool, light wetsuit smart |
| March | 73-75°F | 23-24°C | Warming up, rash guard works for most |
| April | 76-78°F | 24-26°C | Comfortable, no wetsuit needed |
| May | 79-81°F | 26-27°C | Warm, great visibility |
| June | 82-84°F | 28-29°C | Peak snorkel season begins |
| July | 84-86°F | 29-30°C | Warmest water of the year |
| August | 84-86°F | 29-30°C | Hot water, afternoon thunderstorms possible |
| September | 83-85°F | 28-29°C | Still very warm, storm season |
| October | 80-82°F | 27-28°C | Excellent conditions, crowds thin out |
| November | 76-79°F | 24-26°C | Cooling down, light wetsuit optional |
| December | 72-75°F | 22-24°C | Winter chill, 3mm wetsuit recommended |
What wetsuit do I need in Key Largo?
Summer (June-October): No wetsuit needed for most people. A rash guard protects against sun and light stings from jellyfish.
Spring/Fall (April-May, November): A 1-2mm shorty is comfortable for longer dives. Snorkelers usually skip it.
Winter (December-March): A 3mm full wetsuit makes a real difference, especially for divers spending 45+ minutes underwater. Water in the low 70s feels cold on repeat dives.
If you are diving with Silent World, the shop has wetsuits available for rent if you do not bring your own.
Is the water warm enough to snorkel year-round in Key Largo?
Yes – Key Largo is snorkelable every month of the year. Even in January and February when temps dip to 70°F, most guests snorkel comfortably, especially in a wetsuit or with the physical activity of swimming keeping them warm. Silent World runs snorkeling tours seven days a week, weather permitting, year-round.
The sweet spot for first-time visitors who want warm water and good conditions without peak-season crowds is late April through June or October through early November.
Want to know the best time to book your trip? Silent World runs daily snorkel tours to Key Largo’s best reefs – small boats, no crowds, gear included.
Essential FAQs: Key Largo Water Temperature
Water temps in Key Largo typically run 70-72F in winter (Jan-Feb), 76-82F in spring and fall, and 84-86F in midsummer. For the most current reading, check NOAA nearshore water temp data for Key Largo.
Around 72-75F – that is warm relative to most of the US, but you will want a 3mm wetsuit for anything more than a quick snorkel, especially if you get cold easily.
May, June, and October tend to hit the best combination of warm water, calm seas, and good visibility. July and August are warmest but come with afternoon storms that can shorten trips.
The water gets cooler (low 70s F) but never cold in the way northern Atlantic water gets cold. Air temps stay in the 65-75F range in winter. It is mild, not frigid.
Florida Keys water averages around 79F year-round. Key Largo specifically runs slightly warmer in summer (84-86F) and slightly cooler in winter (70-72F) depending on Gulf Stream proximity.
Not in summer. From June through October, the water is 82-86F and most people snorkel in just a bathing suit. A rash guard is always a good idea for sun protection. In winter, a 3mm wetsuit makes the experience significantly more comfortable.
Related reading: How to snorkel and What kind of wetsuit to wear in Key Largo.