Gold Coast
Key Biscayne Water Temperature
Cape Florida, Stiltsville, and the top of the Biscayne flats.
Sea-surface temperature
WarmHolding steady · last two weeks
That is about 2°F warmer than average for this time of year, and holding steady over the last two weeks. The November average here is 79°F.
Updated Saturday, November 7 — sea-surface temperature modeled for Key Biscayne by Open-Meteo.
Out in the open Gulf, NOAA buoy VAKF1 — 4 miles offshore — is reading 81°F. Deep water offshore runs cooler than the shallows in summer and warmer in winter, so it won't match the beach.
For swimming
Warm
About as good as it gets — warm enough to stay in for hours without getting chilled.
For fishing
Peak season
Snook, redfish and tarpon are all active and feeding. The tarpon migration through the passes runs at the upper end of this range.
The last two weeks
| Date | Average |
|---|---|
| Oct 25 | 82°F |
| Oct 26 | 82°F |
| Oct 27 | 82°F |
| Oct 28 | 81.3°F |
| Oct 29 | 81.3°F |
| Oct 30 | 81.5°F |
| Oct 31 | 81.3°F |
| Nov 1 | 81°F |
| Nov 2 | 80.4°F |
| Nov 3 | 80.2°F |
| Nov 4 | 80.1°F |
| Nov 5 | 80.4°F |
| Nov 6 | 81°F |
| Nov 7 | 81.3°F |
Key Biscayne water temperature by month
Averaged from 3 years of daily sea-surface temperature (2023–2025). The range column is the coolest and warmest daily average recorded in that month over the period — a guide to how much any given year can differ, not a record high and low.
| Month | Range | Average |
|---|---|---|
JanJanuary Cool but comfortable | 69–77°F | 73°F |
FebFebruary Warm | 72–80°F | 75°F |
MarMarch Warm | 73–82°F | 77°F |
AprApril Warm | 75–84°F | 79°F |
MayMay Very warm | 77–88°F | 84°F |
JunJune Very warm | 84–88°F | 86°F |
JulJuly Bath water | 86–92°F | 89°F |
AugAugust Bath water | 86–91°F | 89°F |
SepSeptember Very warm | 84–90°F | 87°F |
OctOctober Very warm | 80–87°F | 83°F |
NovNovembernow Warm | 76–81°F | 79°F |
DecDecember Warm | 72–80°F | 76°F |
Warmest
89°FJuly
Coolest
73°FJanuary
Warmest on average in July at 89°F; coolest in January at 73°F.
The water at Key Biscayne
Key Biscayne is where Biscayne Bay's famous flats begin — hard bottom and turtle grass running south past Stiltsville toward the park, holding bonefish, permit, and tarpon within sight of the Miami skyline. Cape Florida at the island's south end gives land-based access to a productive shoreline, and the reef and Fowey Rocks light sit just outside for snapper and grouper.
Cape Florida & the bay's ocean side
What moves the water temperature here
The Gulf shelf off this coast is shallow, which is why the water swings so much more between summer and winter than open ocean at the same latitude does. Shallow water heats fast and gives that heat up fast: a single strong winter cold front can pull the inshore bays several degrees down in a couple of days, while the beaches a mile offshore barely move. Wind direction matters too — a sustained offshore breeze can pull cooler water up from below and drop the beach temperature noticeably in a morning.
Inshore bays, canals and flats run warmer than the beach through the summer and colder through the winter, for the same reason. The reading above is for the open water at Key Biscayne; expect the back bays to be a few degrees either side of it depending on the season.
Common questions
- What is the water temperature at Key Biscayne right now?
- The water at Key Biscayne is currently about 81°F (27°C). The November average here is 79°F.
- Is the water warm enough to swim at Key Biscayne in November?
- November averages 79°F at Key Biscayne, which most people would call warm. About as good as it gets — warm enough to stay in for hours without getting chilled.
- When is the water warmest at Key Biscayne?
- July is the warmest month on average at 89°F, and January the coolest at 73°F. 11 months of the year average 75°F or above.
- Why does the water temperature change so quickly here?
- The Gulf shelf off this coast is shallow, so it heats and cools far faster than deep open ocean. A strong winter cold front can pull the inshore water down several degrees in a couple of days, and a sustained offshore wind can drop beach temperatures in a single morning by pulling cooler water up from below.