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SunnyDays

ERA5 almanac — 8 years of real data

Cancún in December

Cancún in December: 47% of days see measurable rain, 80°F average high, 20% of days historically clear (n=248, ERA5 2018–2025).

Cancún in December is historically a poor month for sun: only 20% of days clear across 8 years (n=248, avg high 80°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 December

Clear-sky percentage for Cancún 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		 22% n=120 80°F
Late December
16th–end		 18% n=128 80°F
Full month average 20% n=248 80°F

Sunshine & warmth in December

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 December. Primary: % of days ≥ 72°F with > 6 h of sunshine.
Period Warm & sunny (≥72°F, >6 h sun) Sample (n)
Early December
1st–15th		 97% n=120
Late December
16th–end		 91% n=128
Full month average 94% n=248
10.4 h median sunshine per day 86% of days exceed 8 h sunshine 47% 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

Cancún is mostly overcast in December historically: only 20% of days are clear across 8 years (n=248), avg high 80°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 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 ← this page 20% n=248 All destinations →

Frequently asked

Does it rain in Cancún in December?

Sometimes. Cancún sees measurable rain on 47% of days in December historically (n=248 days, ERA5 2018–2025) — not frequent enough to plan around, but not negligible either.

Is Cancún good for sun in December?

Not usually. Cancún is historically overcast in December: only 20% of days are clear (avg high 80°F, n=248 days, ERA5 2018–2025). April is historically far better for sun here.

How Cancún compares in December

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.