ERA5 almanac — 8 years of real data

St. Barthélemy in October

St. Barthélemy in October: 57% of days see measurable rain, 83°F average high, 20% of days historically clear (n=248, ERA5 2018–2025).

St. Barthélemy in October is historically a poor month for sun: only 20% of days clear across 8 years (n=248, avg high 83°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 October

Clear-sky percentage for St. Barthélemy 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	21%	n=120	83°F
Late October 16th–end	20%	n=128	83°F
Full month average	20%	n=248	83°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. Barthélemy 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	93%	n=120
Late October 16th–end	94%	n=128
Full month average	94%	n=248

11.5 h median sunshine per day 91% of days exceed 8 h sunshine 57% of days see ≥ 1 mm rain — rain is not hidden

Comparison (old vs new): WMO-code “clear” bar: 20%. Sunshine-based “warm & sunny”: 94%. The 74-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. Barthélemy is mostly overcast in October historically: only 20% of days are clear across 8 years (n=248), avg high 83°F. If you want sun in St. Barthélemy, March is historically much better. Most visitors this month will see more clouds than sun.

→ 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	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 ← this page	20%	n=248	All destinations →
November	19%	n=240	All destinations →
December	18%	n=248	All destinations →

Frequently asked

Does it rain in St. Barthélemy in October?

Yes, frequently. In St. Barthélemy, 57% 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. Barthélemy good for sun in October?

Not usually. St. Barthélemy is historically overcast in October: only 20% of days are clear (avg high 83°F, n=248 days, ERA5 2018–2025). March is historically far better for sun here.

How St. Barthélemy compares in October

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

→ St. Barthélemy vs Mérida in October — Mérida is 20% clear historically
→ St. Barthélemy vs Outer Banks in October — Outer Banks is 20% clear historically
→ St. Barthélemy vs Anguilla in October — Anguilla is 19% clear historically

→ St. Barthélemy 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.