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SunnyDays

ERA5 almanac — 8 years of real data

Jacksonville in May

Jacksonville in May is a mixed month for sun: 41% of days historically clear (n=248, avg high 85°F). The outcome varies year to year — check the early/late split below. 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 Jacksonville 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 May

Clear-sky percentage for Jacksonville in May, split by half-month. “n” is the number of days sampled across 8 years (2018–2025).
Period % Clear days Sample (n) Avg high
Early May
1st–15th		 46% n=120 85°F
Late May
16th–end		 37% n=128 85°F
Full month average 41% n=248 85°F

Sunshine & warmth in May

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 Jacksonville in May. Primary: % of days ≥ 72°F with > 6 h of sunshine.
Period Warm & sunny (≥72°F, >6 h sun) Sample (n)
Early May
1st–15th		 93% n=120
Late May
16th–end		 94% n=128
Full month average 94% n=248
12.5 h median sunshine per day 88% of days exceed 8 h sunshine 33% of days see ≥ 1 mm rain — rain is not hidden
Comparison (old vs new): WMO-code “clear” bar: 41%. Sunshine-based “warm & sunny”: 94%. The 53-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

Jacksonville in May is genuinely mixed: 41% of days historically clear (n=248), avg high 85°F — more cloudy than clear. The outcome varies year to year; don't book if you need guaranteed sun.

Every month in Jacksonville

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

Historical clear-sky % for Jacksonville, all months, ERA5 2018–2025.
Month % Clear Sample (n)
January 9% n=248 All destinations →
February 27% n=226 All destinations →
March 37% n=248 All destinations →
April 48% n=240 All destinations →
May ← this page 41% n=248 All destinations →
June 15% n=240 All destinations →
July 8% n=248 All destinations →
August 7% n=248 All destinations →
September 22% n=240 All destinations →
October 33% n=248 All destinations →
November 24% n=240 All destinations →
December 16% 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.