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SunnyDays

ERA5 almanac comparison — 8 years of real data

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

St. John, USVI edges out Costa Rica — Guanacaste for sun in October: 15% clear historically versus 2% (8-year ERA5 average, a 13-point gap). Costa Rica — Guanacaste also sees measurably more rain than St. John, USVI this month (95% vs 59% 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 October. For this week’s actual forecast, each destination links to its live page below.

Costa Rica — Guanacaste

CR

Clear days, October
2%
Sample size
n=248 days
Avg high
86°F
Early October (1st–15th)
0%
Late October (16th–end)
3%
Rain frequency
95% of days

St. John, USVI

VI

Clear days, October
15%
Sample size
n=248 days
Avg high
80°F
Early October (1st–15th)
18%
Late October (16th–end)
13%
Rain frequency
59% 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.