ERA5 almanac comparison — 8 years of real data
Costa Rica — Guanacaste vs Mexico City: weather in March
Essentially a tie in March: Costa Rica — Guanacaste is 70% clear historically, Mexico City is 71% clear (8-year ERA5 average) — within the noise. Avg high 96°F vs 81°F. Pick based on flight time or price, not weather — the weather won't decide this one for you.
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
Mexico City
MX
- Clear days, March
- 71%
- Sample size
- n=248 days
- Avg high
- 81°F
- Early March (1st–15th)
- 68%
- Late March (16th–end)
- 73%
- Rain frequency
- 10% of days
Compare Costa Rica — Guanacaste vs Mexico City 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.