ERA5 almanac comparison — 8 years of real data
Door County vs St. Augustine: weather in September
Essentially a tie in September: Door County is 18% clear historically, St. Augustine is 17% clear (8-year ERA5 average) — within the noise. Avg high 69°F vs 83°F. St. Augustine also sees measurably more rain than Door County this month (64% vs 32% of days). Pick based on flight time or price, not weather — the weather won't decide this one for you.
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%
- Rain frequency
- 32% of days
St. Augustine
FL
- Clear days, September
- 17%
- Sample size
- n=240 days
- Avg high
- 83°F
- Early September (1st–15th)
- 11%
- Late September (16th–end)
- 23%
- Rain frequency
- 64% of days
Compare Door County vs St. Augustine 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.