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SunnyDays

ERA5 almanac — 8 years of real data

St. John, USVI in March

St. John, USVI in March: 26% of days see measurable rain, 75°F average high, 28% of days historically clear (n=248, ERA5 2018–2025).

St. John, USVI in March is historically a poor month for sun: only 28% of days clear across 8 years (n=248, avg high 75°F). 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 March

Clear-sky percentage for St. John, USVI in March, split by half-month. “n” is the number of days sampled across 8 years (2018–2025).
Period % Clear days Sample (n) Avg high
Early March
1st–15th		 30% n=120 75°F
Late March
16th–end		 27% n=128 75°F
Full month average 28% n=248 75°F

Sunshine & warmth in March

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 March. Primary: % of days ≥ 72°F with > 6 h of sunshine.
Period Warm & sunny (≥72°F, >6 h sun) Sample (n)
Early March
1st–15th		 99% n=120
Late March
16th–end		 100% n=128
Full month average 100% n=248
11.3 h median sunshine per day 99% of days exceed 8 h sunshine 26% of days see ≥ 1 mm rain — rain is not hidden
Comparison (old vs new): WMO-code “clear” bar: 28%. Sunshine-based “warm & sunny”: 100%. The 72-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 mostly overcast in March historically: only 28% of days are clear across 8 years (n=248), avg high 75°F. Most visitors this month will see more clouds than sun.

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 ← this page 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 16% n=248 All destinations →

Frequently asked

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

Sometimes. St. John, USVI sees measurable rain on 26% of days in March 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 March?

Not usually. St. John, USVI is historically overcast in March: only 28% of days are clear (avg high 75°F, n=248 days, ERA5 2018–2025).

How St. John, USVI compares in March

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.