Skip to main content
SunnyDays

ERA5 almanac — 8 years of real data

Asheville in September

Asheville in September is a mixed month for sun: 40% of days historically clear (n=240, avg high 78°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 Asheville 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 September

Clear-sky percentage for Asheville in September, split by half-month. “n” is the number of days sampled across 8 years (2018–2025).
Period % Clear days Sample (n) Avg high
Early September
1st–15th		 41% n=120 78°F
Late September
16th–end		 38% n=120 78°F
Full month average 40% n=240 78°F

Sunshine & warmth in September

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 Asheville in September. Primary: % of days ≥ 72°F with > 6 h of sunshine.
Period Warm & sunny (≥72°F, >6 h sun) Sample (n)
Early September
1st–15th		 92% n=120
Late September
16th–end		 71% n=120
Full month average 82% n=240
11.6 h median sunshine per day 85% of days exceed 8 h sunshine 32% of days see ≥ 1 mm rain — rain is not hidden
Comparison (old vs new): WMO-code “clear” bar: 40%. Sunshine-based “warm & sunny”: 82%. The 42-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

Asheville in September is genuinely mixed: 40% of days historically clear (n=240), avg high 78°F — more cloudy than clear. The outcome varies year to year; don't book if you need guaranteed sun.

Every month in Asheville

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

Historical clear-sky % for Asheville, all months, ERA5 2018–2025.
Month % Clear Sample (n)
January 0% n=248 All destinations →
February 1% n=226 All destinations →
March 3% n=248 All destinations →
April 19% n=240 All destinations →
May 26% n=248 All destinations →
June 30% n=240 All destinations →
July 21% n=248 All destinations →
August 25% n=248 All destinations →
September ← this page 40% n=240 All destinations →
October 23% n=248 All destinations →
November 4% 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.