ERA5 almanac comparison — 8 years of real data
Door County vs Missoula: weather in September
Missoula is the clear winner for sun in September: 57% of days historically clear versus just 18% in Door County — a 39-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 September. For this
week’s actual forecast, each destination links to its live page below.
Door County
WI
- Clear days, September
- 18%
- Sample size
- n=240 days
- Avg high
- 69°F
- Early September (1st–15th)
- 22%
- Late September (16th–end)
- 14%
Missoula
MT
- Clear days, September
- 57%
- Sample size
- n=240 days
- Avg high
- 76°F
- Early September (1st–15th)
- 72%
- Late September (16th–end)
- 42%
Compare Door County vs Missoula 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.