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SunnyDays

ERA5 almanac — 8 years of real data

Mérida in December

Mérida in December: 21% of days see measurable rain, 84°F average high, 53% of days historically clear (n=248, ERA5 2018–2025).

Mérida in December is a mixed month for sun: 53% of days historically clear (n=248, avg high 84°F). The outcome varies year to year — check the early/late split below. 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 Mérida 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 Mérida 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		 58% n=120 84°F
Late December
16th–end		 48% n=128 84°F
Full month average 53% n=248 84°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 Mérida 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		 94% n=120
Late December
16th–end		 91% n=128
Full month average 92% n=248
10.1 h median sunshine per day 85% of days exceed 8 h sunshine 21% of days see ≥ 1 mm rain — rain is not hidden
Comparison (old vs new): WMO-code “clear” bar: 53%. Sunshine-based “warm & sunny”: 92%. The 39-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

Mérida in December is genuinely mixed: 53% of days historically clear (n=248), avg high 84°F — roughly even odds. The outcome varies year to year; don't book if you need guaranteed sun.

Every month in Mérida

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

Historical clear-sky % for Mérida, all months, ERA5 2018–2025.
Month % Clear Sample (n)
January 55% n=248 All destinations →
February 61% n=226 All destinations →
March 74% n=248 All destinations →
April 68% n=240 All destinations →
May 47% n=248 All destinations →
June 20% n=240 All destinations →
July 20% n=248 All destinations →
August 13% n=248 All destinations →
September 8% n=240 All destinations →
October 20% n=248 All destinations →
November 38% n=240 All destinations →
December ← this page 53% n=248 All destinations →

Frequently asked

Does it rain in Mérida in December?

Sometimes. Mérida sees measurable rain on 21% of days in December historically (n=248 days, ERA5 2018–2025) — not frequent enough to plan around, but not negligible either.

Is Mérida good for sun in December?

It's mixed. Mérida in December is clear on 53% of days historically (avg high 84°F, n=248 days, ERA5 2018–2025) — the outcome varies year to year.

How Mérida compares in December

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