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SunnyDays

ERA5 almanac — 8 years of real data

Sea Island in June

Sea Island in June is historically a poor month for sun: only 24% of days clear across 8 years (n=240, avg high 85°F). October is the clearest month for Sea 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 Sea 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 June

Clear-sky percentage for Sea Island in June, split by half-month. “n” is the number of days sampled across 8 years (2018–2025).
Period % Clear days Sample (n) Avg high
Early June
1st–15th		 24% n=120 85°F
Late June
16th–end		 25% n=120 85°F
Full month average 24% n=240 85°F

Sunshine & warmth in June

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 Sea Island in June. Primary: % of days ≥ 72°F with > 6 h of sunshine.
Period Warm & sunny (≥72°F, >6 h sun) Sample (n)
Early June
1st–15th		 91% n=120
Late June
16th–end		 97% n=120
Full month average 94% n=240
12.3 h median sunshine per day 90% of days exceed 8 h sunshine 52% of days see ≥ 1 mm rain — rain is not hidden
Comparison (old vs new): WMO-code “clear” bar: 24%. Sunshine-based “warm & sunny”: 94%. The 70-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

Sea Island is mostly overcast in June historically: only 24% of days are clear across 8 years (n=240), avg high 85°F. If you want sun in Sea Island, October is historically much better. Most visitors this month will see more clouds than sun.

→ See all destinations in October — historically the best month for sun in Sea Island.

Every month in Sea Island

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

Historical clear-sky % for Sea Island, all months, ERA5 2018–2025.
Month % Clear Sample (n)
January 2% n=248 All destinations →
February 8% n=226 All destinations →
March 15% n=248 All destinations →
April 36% n=240 All destinations →
May 36% n=248 All destinations →
June ← this page 24% n=240 All destinations →
July 14% n=248 All destinations →
August 7% n=248 All destinations →
September 32% n=240 All destinations →
October 42% n=248 All destinations →
November 17% n=240 All destinations →
December 7% 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.