ERA5 almanac comparison — 8 years of real data
Park City vs Wine Country Sonoma: weather in September
Wine Country Sonoma is the clear winner for sun in September: 86% of days historically clear versus just 30% in Park City — a 56-point gap across 8 years of ERA5 data. Park City also sees measurably more rain than Wine Country Sonoma this month (32% vs 5% of days). 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.
Park City
UT
- Clear days, September
- 30%
- Sample size
- n=240 days
- Avg high
- 70°F
- Early September (1st–15th)
- 41%
- Late September (16th–end)
- 19%
- Rain frequency
- 32% of days
Wine Country Sonoma
CA
- Clear days, September
- 86%
- Sample size
- n=240 days
- Avg high
- 84°F
- Early September (1st–15th)
- 92%
- Late September (16th–end)
- 81%
- Rain frequency
- 5% of days
Compare Park City vs Wine Country Sonoma 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.