ERA5 almanac — 8 years of real data

Cancún in January

Cancún in January: rain frequency data not yet backfilled for this month, 79°F average high, 21% of days historically clear (n=248, ERA5 2018–2025).

Cancún in January is historically a poor month for sun: only 21% of days clear across 8 years (n=248, avg high 79°F). April is the clearest month for Cancún 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 Cancún 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 Cancún 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	22%	n=120	79°F
Late January 16th–end	21%	n=128	79°F
Full month average	21%	n=248	79°F

Bottom line

Cancún is mostly overcast in January historically: only 21% of days are clear across 8 years (n=248), avg high 79°F. If you want sun in Cancún, April is historically much better. Most visitors this month will see more clouds than sun.

→ See all destinations in April — historically the best month for sun in Cancún.

Every month in Cancún

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

Historical clear-sky % for Cancún, all months, ERA5 2018–2025.
Month	% Clear	Sample (n)
January ← this page	21%	n=248	All destinations →
February	22%	n=226	All destinations →
March	34%	n=248	All destinations →
April	40%	n=240	All destinations →
May	21%	n=248	All destinations →
June	10%	n=240	All destinations →
July	11%	n=248	All destinations →
August	9%	n=248	All destinations →
September	5%	n=240	All destinations →
October	10%	n=248	All destinations →
November	15%	n=240	All destinations →
December	20%	n=248	All destinations →

Frequently asked

Is Cancún good for sun in January?

Not usually. Cancún is historically overcast in January: only 21% of days are clear (avg high 79°F, n=248 days, ERA5 2018–2025). April is historically far better for sun here.

→ Cancún 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.