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SunnyDays

ERA5 almanac — 8 years of real data

Hilton Head in August

Hilton Head in August is historically a poor month for sun: only 9% of days clear across 8 years (n=248, avg high 86°F). October is the clearest month for Hilton Head 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 Hilton Head 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 August

Clear-sky percentage for Hilton Head in August, split by half-month. “n” is the number of days sampled across 8 years (2018–2025).
Period % Clear days Sample (n) Avg high
Early August
1st–15th		 6% n=120 86°F
Late August
16th–end		 12% n=128 86°F
Full month average 9% n=248 86°F

Bottom line

Hilton Head is a poor choice for sun in August: just 9% of days clear historically (n=248). October is the historically strongest month for sun here. The 8-year record is consistent — this is not a fluke bad stretch.

→ See all destinations in October — historically the best month for sun in Hilton Head.

Every month in Hilton Head

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

Historical clear-sky % for Hilton Head, all months, ERA5 2018–2025.
Month % Clear Sample (n)
January 0% n=248 All destinations →
February 10% n=226 All destinations →
March 19% n=248 All destinations →
April 38% n=240 All destinations →
May 39% n=248 All destinations →
June 20% n=240 All destinations →
July 15% n=248 All destinations →
August ← this page 9% n=248 All destinations →
September 33% n=240 All destinations →
October 45% n=248 All destinations →
November 12% n=240 All destinations →
December 6% 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.