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SunnyDays

ERA5 almanac — 8 years of real data

Cayman Islands in December

Cayman Islands in December: 51% of days see measurable rain, 82°F average high, 12% of days historically clear (n=248, ERA5 2018–2025).

Cayman Islands in December is historically a poor month for sun: only 12% of days clear across 8 years (n=248, avg high 82°F). January is the clearest month for Cayman Islands 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 Cayman Islands 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 Cayman Islands 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		 13% n=120 82°F
Late December
16th–end		 12% n=128 82°F
Full month average 12% n=248 82°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 Cayman Islands 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		 95% n=128
Full month average 96% n=248
10.8 h median sunshine per day 94% of days exceed 8 h sunshine 51% of days see ≥ 1 mm rain — rain is not hidden
Comparison (old vs new): WMO-code “clear” bar: 12%. Sunshine-based “warm & sunny”: 96%. The 84-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

Cayman Islands is a poor choice for sun in December: just 12% of days clear historically (n=248). January 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 January — historically the best month for sun in Cayman Islands.

Every month in Cayman Islands

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

Historical clear-sky % for Cayman Islands, all months, ERA5 2018–2025.
Month % Clear Sample (n)
January 19% n=248 All destinations →
February 11% n=226 All destinations →
March 17% n=248 All destinations →
April 10% n=240 All destinations →
May 5% n=248 All destinations →
June 4% n=240 All destinations →
July 2% n=248 All destinations →
August 4% n=248 All destinations →
September 4% n=240 All destinations →
October 5% n=248 All destinations →
November 12% n=240 All destinations →
December ← this page 12% n=248 All destinations →

Frequently asked

Does it rain in Cayman Islands in December?

Yes, frequently. In Cayman Islands, 51% of days in December 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 Cayman Islands good for sun in December?

Not usually. Cayman Islands is historically overcast in December: only 12% of days are clear (avg high 82°F, n=248 days, ERA5 2018–2025). January is historically far better for sun here.

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.