ERA5 almanac comparison — 8 years of real data
Boundary Waters vs Martha's Vineyard: weather in May
Boundary Waters edges out Martha's Vineyard for sun in May: 10% clear historically versus 3% (8-year ERA5 average, a 7-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 May. For this
week’s actual forecast, each destination links to its live page below.
Boundary Waters
MN
- Clear days, May
- 10%
- Sample size
- n=248 days
- Avg high
- 64°F
- Early May (1st–15th)
- 8%
- Late May (16th–end)
- 12%
Martha's Vineyard
MA
- Clear days, May
- 3%
- Sample size
- n=248 days
- Avg high
- 62°F
- Early May (1st–15th)
- 1%
- Late May (16th–end)
- 4%
Compare Boundary Waters vs Martha's Vineyard 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.