ERA5 almanac comparison — 8 years of real data
Big Sky vs Sun Valley: weather in August
Sun Valley is the clear winner for sun in August: 58% of days historically clear versus just 18% in Big Sky — a 40-point gap across 8 years of ERA5 data. This isn't close.
What you are reading: 8-year historical averages, not a forecast.
Either destination can still surprise you this specific August. For this
week’s actual forecast, each destination links to its live page below.
Big Sky
MT
- Clear days, August
- 18%
- Sample size
- n=248 days
- Avg high
- 70°F
- Early August (1st–15th)
- 20%
- Late August (16th–end)
- 16%
Sun Valley
ID
- Clear days, August
- 58%
- Sample size
- n=248 days
- Avg high
- 80°F
- Early August (1st–15th)
- 63%
- Late August (16th–end)
- 54%
Compare Big Sky vs Sun Valley in another month
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.