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SunnyDays

ERA5 almanac — 8 years of real data

Nashville in May

Nashville in May is historically a poor month for sun: only 28% of days clear across 8 years (n=248, avg high 79°F). September is the clearest month for Nashville 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 Nashville 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 Nashville 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		 23% n=120 79°F
Late May
16th–end		 33% n=128 79°F
Full month average 28% n=248 79°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 Nashville 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		 62% n=120
Late May
16th–end		 84% n=128
Full month average 73% n=248
11.8 h median sunshine per day 76% of days exceed 8 h sunshine 47% of days see ≥ 1 mm rain — rain is not hidden
Comparison (old vs new): WMO-code “clear” bar: 28%. Sunshine-based “warm & sunny”: 73%. The 45-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

Nashville is mostly overcast in May historically: only 28% of days are clear across 8 years (n=248), avg high 79°F. If you want sun in Nashville, September is historically much better. Most visitors this month will see more clouds than sun.

→ See all destinations in September — historically the best month for sun in Nashville.

Every month in Nashville

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

Historical clear-sky % for Nashville, all months, ERA5 2018–2025.
Month % Clear Sample (n)
January 0% n=248 All destinations →
February 1% n=226 All destinations →
March 8% n=248 All destinations →
April 18% n=240 All destinations →
May ← this page 28% n=248 All destinations →
June 30% n=240 All destinations →
July 19% n=248 All destinations →
August 32% n=248 All destinations →
September 48% n=240 All destinations →
October 32% n=248 All destinations →
November 6% n=240 All destinations →
December 0% 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.