ERA5 almanac comparison — 8 years of real data
Birmingham vs Costa Rica — Guanacaste: weather in December
Costa Rica — Guanacaste is the clear winner for sun in December: 62% of days historically clear versus just 1% in Birmingham — a 61-point gap across 8 years of ERA5 data. Birmingham also sees measurably more rain than Costa Rica — Guanacaste this month (33% vs 15% 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 December. For this
week’s actual forecast, each destination links to its live page below.
Birmingham
AL
- Clear days, December
- 1%
- Sample size
- n=248 days
- Avg high
- 58°F
- Early December (1st–15th)
- 1%
- Late December (16th–end)
- 1%
- Rain frequency
- 33% of days
Costa Rica — Guanacaste
CR
- Clear days, December
- 62%
- Sample size
- n=248 days
- Avg high
- 89°F
- Early December (1st–15th)
- 64%
- Late December (16th–end)
- 61%
- Rain frequency
- 15% of days
Compare Birmingham vs Costa Rica — Guanacaste 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.