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SunnyDays

ERA5 almanac — 8 years of real data

Amelia Island in September

Amelia Island in September is historically a poor month for sun: only 22% of days clear across 8 years (n=240, avg high 84°F). April is the clearest month for Amelia Island historically. Historical average, not a forecast.

What you are reading: 8-year historical averages from the ERA5 reanalysis, not a forecast. A month that is historically 90% clear can still be overcast on your specific trip. For this week’s actual forecast, see the live Amelia Island page. Both can be true at once: “historically strong in this month; this particular week is not.” We label which is which.

Early vs. Late September

Clear-sky percentage for Amelia Island in September, split by half-month. “n” is the number of days sampled across 8 years (2018–2025).
Period % Clear days Sample (n) Avg high
Early September
1st–15th		 17% n=120 84°F
Late September
16th–end		 27% n=120 84°F
Full month average 22% n=240 84°F

Sunshine & warmth in September

A second measure using actual sunshine hours (ERA5 sunshine_duration), not the daily weather code. A Lowcountry day with 12 hours of sun and a 25-minute afternoon storm is counted below as a warm, sunny day — because it was. How we define this.

Sunshine-based metrics for Amelia Island in September. Primary: % of days ≥ 72°F with > 6 h of sunshine.
Period Warm & sunny (≥72°F, >6 h sun) Sample (n)
Early September
1st–15th		 86% n=120
Late September
16th–end		 87% n=120
Full month average 86% n=240
11.2 h median sunshine per day 82% of days exceed 8 h sunshine 62% of days see ≥ 1 mm rain — rain is not hidden
Comparison (old vs new): WMO-code “clear” bar: 22%. Sunshine-based “warm & sunny”: 86%. The 64-point gap is from brief afternoon convective storms that stamp the whole day as “rain” in the WMO code but leave the bulk of the sunshine untouched.

Bottom line

Amelia Island is mostly overcast in September historically: only 22% of days are clear across 8 years (n=240), avg high 84°F. If you want sun in Amelia Island, April is historically much better. Most visitors this month will see more clouds than sun.

→ See all destinations in April — historically the best month for sun in Amelia Island.

Every month in Amelia Island

Compare across all months with data. Numbers are historical clear-sky %.

Historical clear-sky % for Amelia Island, all months, ERA5 2018–2025.
Month % Clear Sample (n)
January 7% n=248 All destinations →
February 22% n=226 All destinations →
March 25% n=248 All destinations →
April 46% n=240 All destinations →
May 38% n=248 All destinations →
June 18% n=240 All destinations →
July 10% n=248 All destinations →
August 9% n=248 All destinations →
September ← this page 22% n=240 All destinations →
October 34% n=248 All destinations →
November 20% n=240 All destinations →
December 12% n=248 All destinations →

All percentages are historical averages from the ERA5 reanalysis via Open-Meteo, 8 full years (2018–2025). “Clear” means avg high ≥ 72 °F, precipitation < 1 mm, and a non-precipitation weather code. This is history, not a forecast. The live 7-day outlook for any destination is on its own page and may differ from the long-run average. Data from Open-Meteo.