ERA5 almanac comparison — 8 years of real data
St. Martin vs Tulum: weather in December
Tulum edges out St. Martin for sun in December: 21% clear historically versus 15% (8-year ERA5 average, a 6-point gap). Both are viable — Tulum 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.
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%
- Rain frequency
- 39% of days
Tulum
MX
- Clear days, December
- 21%
- Sample size
- n=248 days
- Avg high
- 81°F
- Early December (1st–15th)
- 21%
- Late December (16th–end)
- 21%
- Rain frequency
- 49% of days
Compare St. Martin vs Tulum 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.