ERA5 almanac comparison — 8 years of real data
Costa Rica — Guanacaste vs St. Martin: weather in October
St. Martin edges out Costa Rica — Guanacaste for sun in October: 18% clear historically versus 2% (8-year ERA5 average, a 16-point gap). Costa Rica — Guanacaste also sees measurably more rain than St. Martin this month (95% vs 53% of days). 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 October. For this
week’s actual forecast, each destination links to its live page below.
Costa Rica — Guanacaste
CR
- Clear days, October
- 2%
- Sample size
- n=248 days
- Avg high
- 86°F
- Early October (1st–15th)
- 0%
- Late October (16th–end)
- 3%
- Rain frequency
- 95% of days
St. Martin
SX
- Clear days, October
- 18%
- Sample size
- n=248 days
- Avg high
- 80°F
- Early October (1st–15th)
- 19%
- Late October (16th–end)
- 17%
- Rain frequency
- 53% of days
Compare Costa Rica — Guanacaste 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.