ERA5 almanac comparison — 8 years of real data
Boundary Waters vs Montauk: weather in September
Boundary Waters edges out Montauk for sun in September: 20% clear historically versus 10% (8-year ERA5 average, a 10-point gap). Both are viable — Boundary Waters is the safer bet.
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.
Boundary Waters
MN
- Clear days, September
- 20%
- Sample size
- n=240 days
- Avg high
- 68°F
- Early September (1st–15th)
- 22%
- Late September (16th–end)
- 18%
Montauk
NY
- Clear days, September
- 10%
- Sample size
- n=240 days
- Avg high
- 70°F
- Early September (1st–15th)
- 18%
- Late September (16th–end)
- 3%
Compare Boundary Waters vs Montauk 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.