ERA5 almanac comparison — 8 years of real data
New York City vs St. John, USVI: weather in September
New York City edges out St. John, USVI for sun in September: 40% clear historically versus 15% (8-year ERA5 average, a 25-point gap). St. John, USVI also sees measurably more rain than New York City this month (56% vs 34% of days). Both are viable — New York City is the safer bet.
What you are reading: 8-year historical averages, not a forecast.
Either destination can still surprise you this specific September. For this
week’s actual forecast, each destination links to its live page below.
New York City
NY
- Clear days, September
- 40%
- Sample size
- n=240 days
- Avg high
- 76°F
- Early September (1st–15th)
- 41%
- Late September (16th–end)
- 38%
- Rain frequency
- 34% of days
St. John, USVI
VI
- Clear days, September
- 15%
- Sample size
- n=240 days
- Avg high
- 80°F
- Early September (1st–15th)
- 16%
- Late September (16th–end)
- 14%
- Rain frequency
- 56% of days
Compare New York City 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.