ERA5 almanac — 8 years of real data

St. Barthélemy in January

St. Barthélemy in January: rain frequency data not yet backfilled for this month, 79°F average high, 18% of days historically clear (n=248, ERA5 2018–2025).

St. Barthélemy in January is historically a poor month for sun: only 18% of days clear across 8 years (n=248, avg high 79°F). March is the clearest month for St. Barthélemy 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. Barthélemy 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 January

Clear-sky percentage for St. Barthélemy in January, split by half-month. “n” is the number of days sampled across 8 years (2018–2025).
Period	% Clear days	Sample (n)	Avg high
Early January 1st–15th	20%	n=120	79°F
Late January 16th–end	16%	n=128	79°F
Full month average	18%	n=248	79°F

Bottom line

St. Barthélemy is a poor choice for sun in January: just 18% 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. Barthélemy.

Every month in St. Barthélemy

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

Historical clear-sky % for St. Barthélemy, all months, ERA5 2018–2025.
Month	% Clear	Sample (n)
January ← this page	18%	n=248	All destinations →
February	12%	n=226	All destinations →
March	29%	n=248	All destinations →
April	22%	n=240	All destinations →
May	21%	n=248	All destinations →
June	19%	n=240	All destinations →
July	10%	n=248	All destinations →
August	14%	n=248	All destinations →
September	13%	n=240	All destinations →
October	20%	n=248	All destinations →
November	19%	n=240	All destinations →
December	18%	n=248	All destinations →

Frequently asked

Is St. Barthélemy good for sun in January?

Not usually. St. Barthélemy is historically overcast in January: only 18% of days are clear (avg high 79°F, n=248 days, ERA5 2018–2025). March is historically far better for sun here.

→ St. Barthélemy live forecast — this week’s actual 7-day weather, not historical
→ Best destinations in January — all destinations ranked by January 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.