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SunnyDays

ERA5 almanac comparison — 8 years of real data

Costa Rica — Guanacaste vs St. John, USVI: weather in June

St. John, USVI edges out Costa Rica — Guanacaste for sun in June: 20% clear historically versus 5% (8-year ERA5 average, a 15-point gap). Costa Rica — Guanacaste also sees measurably more rain than St. John, USVI this month (88% vs 40% of days). Both are viable — St. John, USVI is the safer bet.

What you are reading: 8-year historical averages, not a forecast. Either destination can still surprise you this specific June. For this week’s actual forecast, each destination links to its live page below.

Costa Rica — Guanacaste

CR

Clear days, June
5%
Sample size
n=240 days
Avg high
87°F
Early June (1st–15th)
1%
Late June (16th–end)
9%
Rain frequency
88% of days

St. John, USVI

VI

Clear days, June
20%
Sample size
n=240 days
Avg high
78°F
Early June (1st–15th)
21%
Late June (16th–end)
20%
Rain frequency
40% of days

Compare Costa Rica — Guanacaste vs St. John, USVI 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.