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SunnyDays

ERA5 almanac — 8 years of real data

Vail in August

Vail in August is a mixed month for sun: 46% of days historically clear (n=248, avg high 76°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 Vail 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 Vail 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		 48% n=120 76°F
Late August
16th–end		 44% n=128 76°F
Full month average 46% n=248 76°F

Sunshine & warmth in August

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 Vail in August. Primary: % of days ≥ 72°F with > 6 h of sunshine.
Period Warm & sunny (≥72°F, >6 h sun) Sample (n)
Early August
1st–15th		 91% n=120
Late August
16th–end		 70% n=128
Full month average 80% n=248
13.1 h median sunshine per day 98% of days exceed 8 h sunshine 26% of days see ≥ 1 mm rain — rain is not hidden
Comparison (old vs new): WMO-code “clear” bar: 46%. Sunshine-based “warm & sunny”: 80%. The 34-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

Vail in August is genuinely mixed: 46% of days historically clear (n=248), avg high 76°F — roughly even odds. The outcome varies year to year; don't book if you need guaranteed sun.

Every month in Vail

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

Historical clear-sky % for Vail, all months, ERA5 2018–2025.
Month % Clear Sample (n)
January 0% n=248 All destinations →
February 0% n=226 All destinations →
March 0% n=248 All destinations →
April 0% n=240 All destinations →
May 0% n=248 All destinations →
June 30% n=240 All destinations →
July 36% n=248 All destinations →
August ← this page 46% n=248 All destinations →
September 23% n=240 All destinations →
October 0% n=248 All destinations →
November 0% 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.