ERA5 almanac comparison — 8 years of real data
Boston vs Exuma: weather in September
Boston edges out Exuma for sun in September: 31% clear historically versus 20% (8-year ERA5 average, a 11-point gap). Both are viable — Boston 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.
Boston
MA
- Clear days, September
- 31%
- Sample size
- n=240 days
- Avg high
- 74°F
- Early September (1st–15th)
- 38%
- Late September (16th–end)
- 24%
Exuma
BS
- Clear days, September
- 20%
- Sample size
- n=240 days
- Avg high
- 85°F
- Early September (1st–15th)
- 24%
- Late September (16th–end)
- 17%
Compare Boston vs Exuma 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.