Amelia Island water temperature in September
Key facts
The Atlantic off Amelia Island averages 82.4°F in September — bath-warm. No cooling effect at all — shade and water matter more than the sea. That is 9.8°F above the island’s annual average of 72.6°F, and 2.2°F down from August.
- Average daily high to low
- Ocean temperature
September in the water
September holds nearly all of August's warmth while the crowds go home, which makes it the best swimming month on the island by any honest reckoning. The trade-off is that it is also the peak of the hurricane season and the wettest month, so surf can be up and rip risk higher.
At 82.4°F the sea is 9.8°F above the island’s annual average of 72.6°F. The air reaches 86°F in September, a gap of 3.6°F, small enough that the ocean gives you no relief from the heat.
What to wear
Nothing needed, and neoprene would be actively unpleasant.
Where this number comes from
82.4°F is the mean of every hourly reading for September across 2023, 2024 and 2025 at NOAA CO-OPS station 8720218, Mayport (Bar Pilots Dock), FL — about 30 km south of the island. The Fernandina Beach station on the island has no water-temperature sensor, so no on-island long record exists to average. We would rather say that plainly than publish an on-island figure we cannot support.
A monthly mean is not a forecast. The real ocean in any given September week moves several degrees around this figure, and a hard south-westerly can pull colder water up onto the shelf in a day. For the reading right now, the offshore waverider buoy 41112 (Offshore Fernandina Beach, FL, 17 km ENE) reports water temperature alongside wave height — that is what feeds our surf report and beach conditions.
September against the months either side
| August | September | October | |
|---|---|---|---|
| Sea temperature | 84.6°F | 82.4°F | 76°F |
| Our reading | Bath-warm | Bath-warm | Warm |
| Air high | 89.5°F | 86°F | 80.1°F |
The annual mean is 72.6°F, and the sea lags the air by about two months in both directions — see water temperature by month for why that lag matters more than the raw number.
One rule for the beach in September
Sea turtle nesting season runs 1 May to 31 October under FWC rules, and September falls inside it. Fill in every hole, take all gear off the beach overnight, keep lights off the sand and stay well clear of marked nests. See sea turtles on Amelia Island.
Next and previous months
Planning a September beach day
Part of Amelia Island water temperature by month.
Frequently asked questions
- What is the water temperature at Amelia Island in September?
- The ocean averages 82.4°F (28.0°C) in September, from three years of hourly NOAA readings at the nearest sensor with a long record — station 8720218, 30 km south of the island. A given week moves several degrees around that.
- Can you swim at Amelia Island in September?
- Bath-warm at 82.4°F. No cooling effect at all — shade and water matter more than the sea.
- Do you need a wetsuit at Amelia Island in September?
- Nothing needed, and neoprene would be actively unpleasant.