Spring or autumn on Amelia Island?
Key facts
Autumn, if you intend to swim: October alone gives you a 76.0°F ocean under 80.1°F air with the crowds gone. Spring wins on air and rainfall — April is the driest month of the year — but the sea is still 71.2°F in April and only reaches 77.7°F in May.
Our verdict
Come in October if getting in the water matters. Come in April if it does not — the air, the rainfall and the trails are all better, and you will not miss the ocean you were not going to swim in. Avoid September unless you are comfortable with hurricane season and the wettest month of the year, and avoid November if you want to swim at all.
Side by side
| Spring (March–May) | Autumn (September–November) | |
|---|---|---|
| Average high | March 72.2°F · April 77.4°F · May 83.9°F | September 86.0°F · October 80.1°F · November 72.4°F |
| Ocean temperature | 64.7°F → 77.7°F | 82.4°F → 70.4°F |
| Rainfall | 3.27″ · 3.03″ · 2.68″ — the driest run of the year | 7.19″ · 4.97″ · 1.87″ — the wettest month and the driest |
| Wet days | 6.0 · 4.7 · 4.3 | 9.1 · 5.2 · 3.7 |
| Humidity | Low until late May | Heavy in September, broken by mid-October |
| Hurricane season | Closed until 1 June | Open throughout, peaking in early September |
| Crowds | Spring break and Concours weekend fill the island | Thin after Labor Day; festival weekends excepted |
| Biting insects | Not yet out in March and April | Present into October near the marsh |
Why the seasons are not mirror images
The air and the ocean peak two months apart, because water holds far more heat than air. The consequence is that spring and autumn are not symmetrical: at the same air temperature, autumn's water is roughly ten degrees warmer than spring's.
| Air high | Ocean | Gap | |
|---|---|---|---|
| April | 77.4°F | 71.2°F | 6.2°F |
| October | 80.1°F | 76.0°F | 4.1°F |
| May | 83.9°F | 77.7°F | 6.2°F |
| September | 86.0°F | 82.4°F | 3.6°F |
That is the whole comparison in one table. Autumn is warmer in the water at every matching point.
Where spring wins outright
Rainfall. May averages 2.68″ across about 4.3 wet days, and April 3.03″ across 4.7. Those are the two driest months of the warm half of the year. September, by contrast, averages 7.19″ across 9.1 wet days — the wettest month.
Humidity. Spring stays dry into late May. September is heavy.
Hurricane season. It runs 1 June to 30 November. All of spring sits outside it; all of autumn sits inside it.
Insects. The marsh is genuinely more pleasant in March and April than in September.
Where autumn wins outright
The water. October's 76.0°F over 80.1°F air is the single best combination the island produces, and it is not close.
Crowds and rates. Demand drops sharply after Labor Day, and October's festival weekends aside, the island is quiet.
The two months to be careful about
September is the peak of hurricane season and the wettest month, and also has the warmest water of the two seasons and the biggest rate drops. People take that trade knowingly — take it with a refundable rate and watch the National Hurricane Center rather than a forecast app. See our hurricane season guide.
March looks like spring on the calendar and is still winter in the water at 64.7°F. It is a trails-and-fort month, not a beach month.
Related pages
Other comparisons
What backs this: NOAA NCEI 1991–2020 monthly normals (station USC00082944) and NOAA CO-OPS water temperatures (station 8720218), in src/data/climate.json.
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