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SunnyDays

ERA5 almanac — 8 years of real data

Jackson Hole in August

Jackson Hole in August is a mixed month for sun: 58% of days historically clear (n=248, avg high 79°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 Jackson Hole 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 Jackson Hole 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		 58% n=120 79°F
Late August
16th–end		 58% n=128 79°F
Full month average 58% n=248 79°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 Jackson Hole 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		 92% n=120
Late August
16th–end		 84% n=128
Full month average 88% n=248
13.2 h median sunshine per day 94% of days exceed 8 h sunshine 17% of days see ≥ 1 mm rain — rain is not hidden
Comparison (old vs new): WMO-code “clear” bar: 58%. Sunshine-based “warm & sunny”: 88%. The 30-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

Jackson Hole in August is genuinely mixed: 58% of days historically clear (n=248), avg high 79°F — more clear than cloudy. The outcome varies year to year; don't book if you need guaranteed sun.

Every month in Jackson Hole

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

Historical clear-sky % for Jackson Hole, 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 3% n=248 All destinations →
June 30% n=240 All destinations →
July 62% n=248 All destinations →
August ← this page 58% n=248 All destinations →
September 34% n=240 All destinations →
October 1% 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.