ERA5 almanac — 8 years of real data

St. Martin in December

St. Martin in December: rain frequency data not yet backfilled for this month, 77°F average high, 15% of days historically clear (n=248, ERA5 2018–2025).

St. Martin in December is historically a poor month for sun: only 15% of days clear across 8 years (n=248, avg high 77°F). March is the clearest month for St. Martin 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. Martin 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. Martin 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	10%	n=120	77°F
Late December 16th–end	20%	n=128	77°F
Full month average	15%	n=248	77°F

Bottom line

St. Martin is a poor choice for sun in December: 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. Martin.

Every month in St. Martin

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

Historical clear-sky % for St. Martin, all months, ERA5 2018–2025.
Month	% Clear	Sample (n)
January	18%	n=248	All destinations →
February	11%	n=226	All destinations →
March	28%	n=248	All destinations →
April	24%	n=240	All destinations →
May	24%	n=248	All destinations →
June	18%	n=240	All destinations →
July	11%	n=248	All destinations →
August	16%	n=248	All destinations →
September	15%	n=240	All destinations →
October	18%	n=248	All destinations →
November	17%	n=240	All destinations →
December ← this page	15%	n=248	All destinations →

Frequently asked

Is St. Martin good for sun in December?

Not usually. St. Martin is historically overcast in December: only 15% of days are clear (avg high 77°F, n=248 days, ERA5 2018–2025). March is historically far better for sun here.

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