ERA5 almanac comparison — 8 years of real data
Portland vs St. Martin: weather in December
St. Martin edges out Portland for sun in December: 15% clear historically versus 0% (8-year ERA5 average, a 15-point gap). Both are viable — St. Martin is the safer bet.
What you are reading: 8-year historical averages, not a forecast.
Either destination can still surprise you this specific December. For this
week’s actual forecast, each destination links to its live page below.
Portland
ME
- Clear days, December
- 0%
- Sample size
- n=248 days
- Avg high
- 38°F
- Early December (1st–15th)
- 0%
- Late December (16th–end)
- 0%
St. Martin
SX
- Clear days, December
- 15%
- Sample size
- n=248 days
- Avg high
- 77°F
- Early December (1st–15th)
- 10%
- Late December (16th–end)
- 20%
Compare Portland vs St. Martin 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.