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SunnyDays

ERA5 almanac comparison — 8 years of real data

Costa Rica — Guanacaste vs Sea Island: weather in May

Sea Island edges out Costa Rica — Guanacaste for sun in May: 36% clear historically versus 9% (8-year ERA5 average, a 27-point gap). Costa Rica — Guanacaste also sees measurably more rain than Sea Island this month (78% vs 36% of days). Both are viable — Sea Island is the safer bet.

What you are reading: 8-year historical averages, not a forecast. Either destination can still surprise you this specific May. For the actual forecast right now, each destination links to its live page below.

Costa Rica — Guanacaste

Costa Rica

Clear days, May
9%
Sample size
n=248 days
Avg high
91°F
Early May (1st–15th)
13%
Late May (16th–end)
5%
Rain frequency
78% of days

Sea Island

GA

Clear days, May
36%
Sample size
n=248 days
Avg high
81°F
Early May (1st–15th)
41%
Late May (16th–end)
31%
Rain frequency
36% of days
See the live forecast →

Frequently asked

Is Costa Rica — Guanacaste or Sea Island warmer in May?

Costa Rica — Guanacaste runs warmer by day in May. Costa Rica — Guanacaste averages highs of 91°F (highs n=248 days); Sea Island averages highs of 81°F (highs n=248 days) (ERA5 2018–2025). Historical averages, not a forecast.

Does it rain more in Costa Rica — Guanacaste or Sea Island in May?

Costa Rica — Guanacaste is measurably wetter than Sea Island. Days with measurable rain: Costa Rica — Guanacaste 78%, Sea Island 36% (n=248 and n=248 days). ERA5 2018–2025; historical, not a forecast.

Which is sunnier in May, Costa Rica — Guanacaste or Sea Island?

Sea Island edges out Costa Rica — Guanacaste for sun in May: 36% clear historically versus 9% (8-year ERA5 average, a 27-point gap). Costa Rica — Guanacaste also sees measurably more rain than Sea Island this month (78% vs 36% of days). Both are viable — Sea Island is the safer bet.

Compare Costa Rica — Guanacaste vs Sea Island 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 forecast for any destination is on its own page and may differ from the long-run average. Data from Open-Meteo.