ERA5 almanac comparison — 8 years of real data
Boston vs Denver: weather in May
Denver edges out Boston for sun in May: 33% clear historically versus 17% (8-year ERA5 average, a 16-point gap). Both are viable — Denver 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.
Boston
MA
- Clear days, May
- 17%
- Sample size
- n=248 days
- Avg high
- 68°F
- Early May (1st–15th)
- 9%
- Late May (16th–end)
- 25%
Denver
CO
- Clear days, May
- 33%
- Sample size
- n=248 days
- Avg high
- 72°F
- Early May (1st–15th)
- 28%
- Late May (16th–end)
- 37%
Compare Boston vs Denver 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.