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SunnyDays

ERA5 almanac — 8 years of real data

Charlotte in May

Charlotte in May is a mixed month for sun: 40% of days historically clear (n=248, avg high 80°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 Charlotte 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 Charlotte 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		 35% n=120 80°F
Late May
16th–end		 45% n=128 80°F
Full month average 40% n=248 80°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 Charlotte 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		 78% n=120
Late May
16th–end		 81% n=128
Full month average 80% n=248
11.9 h median sunshine per day 78% of days exceed 8 h sunshine 37% of days see ≥ 1 mm rain — rain is not hidden
Comparison (old vs new): WMO-code “clear” bar: 40%. Sunshine-based “warm & sunny”: 80%. The 40-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

Charlotte in May is genuinely mixed: 40% of days historically clear (n=248), avg high 80°F — more cloudy than clear. The outcome varies year to year; don't book if you need guaranteed sun.

Every month in Charlotte

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

Historical clear-sky % for Charlotte, all months, ERA5 2018–2025.
Month % Clear Sample (n)
January 0% n=248 All destinations →
February 1% n=226 All destinations →
March 11% n=248 All destinations →
April 36% n=240 All destinations →
May ← this page 40% n=248 All destinations →
June 36% n=240 All destinations →
July 22% n=248 All destinations →
August 23% n=248 All destinations →
September 44% n=240 All destinations →
October 35% n=248 All destinations →
November 6% n=240 All destinations →
December 2% 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.