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SunnyDays

ERA5 almanac — 8 years of real data

St. John, USVI in December

St. John, USVI in December: 44% of days see measurable rain, 76°F average high, 16% of days historically clear (n=248, ERA5 2018–2025).

St. John, USVI in December is historically a poor month for sun: only 16% of days clear across 8 years (n=248, avg high 76°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 December

Clear-sky percentage for St. John, USVI in December, split by half-month. “n” is the number of days sampled across 8 years (2018–2025).
Period % Clear days Sample (n) Avg high
Early December
1st–15th		 12% n=120 76°F
Late December
16th–end		 20% n=128 76°F
Full month average 16% n=248 76°F

Sunshine & warmth in December

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 December. Primary: % of days ≥ 72°F with > 6 h of sunshine.
Period Warm & sunny (≥72°F, >6 h sun) Sample (n)
Early December
1st–15th		 100% n=120
Late December
16th–end		 98% n=128
Full month average 99% n=248
10.7 h median sunshine per day 98% of days exceed 8 h sunshine 44% of days see ≥ 1 mm rain — rain is not hidden
Comparison (old vs new): WMO-code “clear” bar: 16%. Sunshine-based “warm & sunny”: 99%. The 83-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 December: just 16% 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 15% n=248 All destinations →
November 18% n=240 All destinations →
December ← this page 16% n=248 All destinations →

Frequently asked

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

Sometimes. St. John, USVI sees measurable rain on 44% of days in December historically (n=248 days, ERA5 2018–2025) — not frequent enough to plan around, but not negligible either.

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

Not usually. St. John, USVI is historically overcast in December: only 16% of days are clear (avg high 76°F, n=248 days, ERA5 2018–2025). March is historically far better for sun here.

How St. John, USVI compares in December

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.

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.