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SunnyDays

ERA5 almanac — 8 years of real data

Cancún in January

Cancún in January: 50% of days see measurable rain, 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

Sunshine & warmth in January

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 Cancún in January. Primary: % of days ≥ 72°F with > 6 h of sunshine.
Period Warm & sunny (≥72°F, >6 h sun) Sample (n)
Early January
1st–15th		 92% n=120
Late January
16th–end		 92% n=128
Full month average 92% n=248
10.0 h median sunshine per day 85% of days exceed 8 h sunshine 50% of days see ≥ 1 mm rain — rain is not hidden
Comparison (old vs new): WMO-code “clear” bar: 21%. Sunshine-based “warm & sunny”: 92%. The 71-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

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

Does it rain in Cancún in January?

Yes, frequently. In Cancún, 50% of days in January 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 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.

How Cancún compares in January

Head-to-head clear-sky comparisons against destinations travelers plausibly weigh against Cancún 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.