ERA5 almanac comparison — 8 years of real data
Costa Rica — Guanacaste vs Key West: weather in March
Costa Rica — Guanacaste edges out Key West for sun in March: 70% clear historically versus 45% (8-year ERA5 average, a 25-point gap). Both are viable — Costa Rica — Guanacaste is the safer bet.
What you are reading: 8-year historical averages, not a forecast.
Either destination can still surprise you this specific March. For this
week’s actual forecast, each destination links to its live page below.
Costa Rica — Guanacaste
CR
- Clear days, March
- 70%
- Sample size
- n=248 days
- Avg high
- 96°F
- Early March (1st–15th)
- 77%
- Late March (16th–end)
- 63%
- Rain frequency
- 10% of days
Key West
FL
- Clear days, March
- 45%
- Sample size
- n=248 days
- Avg high
- 76°F
- Early March (1st–15th)
- 43%
- Late March (16th–end)
- 47%
- Rain frequency
- 16% of days
Compare Costa Rica — Guanacaste vs Key West 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.