ERA5 almanac comparison — 8 years of real data
Costa Rica — Guanacaste vs Key West: weather in January
Costa Rica — Guanacaste is the clear winner for sun in January: 79% of days historically clear versus just 27% in Key West — a 52-point gap across 8 years of ERA5 data. Key West also sees measurably more rain than Costa Rica — Guanacaste this month (22% vs 6% of days). This isn't close.
What you are reading: 8-year historical averages, not a forecast.
Either destination can still surprise you this specific January. For this
week’s actual forecast, each destination links to its live page below.
Costa Rica — Guanacaste
CR
- Clear days, January
- 79%
- Sample size
- n=248 days
- Avg high
- 91°F
- Early January (1st–15th)
- 72%
- Late January (16th–end)
- 85%
- Rain frequency
- 6% of days
Key West
FL
- Clear days, January
- 27%
- Sample size
- n=248 days
- Avg high
- 72°F
- Early January (1st–15th)
- 32%
- Late January (16th–end)
- 23%
- Rain frequency
- 22% 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.