ERA5 almanac — 8 years of real data

St. John, USVI in October

St. John, USVI in October: 59% of days see measurable rain, 80°F average high, 15% of days historically clear (n=248, ERA5 2018–2025).

St. John, USVI in October is historically a poor month for sun: only 15% of days clear across 8 years (n=248, avg high 80°F). March is the clearest month for St. John, USVI historically. Historical average, not a forecast.

What you are reading: 8-year historical averages from the ERA5 reanalysis, not a forecast. A month that is historically 90% clear can still be overcast on your specific trip. For this week’s actual forecast, see the live St. John, USVI page. Both can be true at once: “historically strong in this month; this particular week is not.” We label which is which.

Early vs. Late October

Clear-sky percentage for St. John, USVI in October, split by half-month. “n” is the number of days sampled across 8 years (2018–2025).
Period	% Clear days	Sample (n)	Avg high
Early October 1st–15th	18%	n=120	80°F
Late October 16th–end	13%	n=128	80°F
Full month average	15%	n=248	80°F

Sunshine & warmth in October

A second measure using actual sunshine hours (ERA5 sunshine_duration), not the daily weather code. A Lowcountry day with 12 hours of sun and a 25-minute afternoon storm is counted below as a warm, sunny day — because it was. How we define this.

Sunshine-based metrics for St. John, USVI in October. Primary: % of days ≥ 72°F with > 6 h of sunshine.
Period	Warm & sunny (≥72°F, >6 h sun)	Sample (n)
Early October 1st–15th	92%	n=120
Late October 16th–end	96%	n=128
Full month average	94%	n=248

11.5 h median sunshine per day 88% of days exceed 8 h sunshine 59% of days see ≥ 1 mm rain — rain is not hidden

Comparison (old vs new): WMO-code “clear” bar: 15%. Sunshine-based “warm & sunny”: 94%. The 79-point gap is from brief afternoon convective storms that stamp the whole day as “rain” in the WMO code but leave the bulk of the sunshine untouched.

Bottom line

St. John, USVI is a poor choice for sun in October: just 15% of days clear historically (n=248). March is the historically strongest month for sun here. The 8-year record is consistent — this is not a fluke bad stretch.

→ See all destinations in March — historically the best month for sun in St. John, USVI.

Every month in St. John, USVI

Compare across all months with data. Numbers are historical clear-sky %.

Historical clear-sky % for St. John, USVI, all months, ERA5 2018–2025.
Month	% Clear	Sample (n)
January	18%	n=248	All destinations →
February	13%	n=226	All destinations →
March	28%	n=248	All destinations →
April	20%	n=240	All destinations →
May	25%	n=248	All destinations →
June	20%	n=240	All destinations →
July	9%	n=248	All destinations →
August	13%	n=248	All destinations →
September	15%	n=240	All destinations →
October ← this page	15%	n=248	All destinations →
November	18%	n=240	All destinations →
December	16%	n=248	All destinations →

Frequently asked

Does it rain in St. John, USVI in October?

Yes, frequently. In St. John, USVI, 59% of days in October see measurable rain, based on 8 years of ERA5 historical data (n=248 days, 2018–2025). This is a historical average, not a forecast.

Is St. John, USVI good for sun in October?

Not usually. St. John, USVI is historically overcast in October: only 15% of days are clear (avg high 80°F, n=248 days, ERA5 2018–2025). March is historically far better for sun here.

How St. John, USVI compares in October

Head-to-head clear-sky comparisons against destinations travelers plausibly weigh against St. John, USVI this month — same passport tier, similar flight distance, both sides from the same 8-year ERA5 record.

→ St. John, USVI vs Turks & Caicos in October — Turks & Caicos is 16% clear historically
→ St. John, USVI vs Shenandoah Valley in October — Shenandoah Valley is 17% clear historically
→ St. John, USVI vs Palm Beach in October — Palm Beach is 18% clear historically

→ St. John, USVI live forecast — this week’s actual 7-day weather, not historical
→ Best destinations in October — all destinations ranked by October clear-sky %
→ All destinations
→ Raw data (JSON) — buckets, n, source

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.