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SunnyDays

ERA5 almanac — 8 years of real data

Honolulu in December

Honolulu in December: 27% of days see measurable rain, 79°F average high, 33% of days historically clear (n=248, ERA5 2018–2025).

Honolulu in December is historically a poor month for sun: only 33% of days clear across 8 years (n=248, avg high 79°F). 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 Honolulu 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 Honolulu 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		 38% n=120 79°F
Late December
16th–end		 29% n=128 79°F
Full month average 33% n=248 79°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 Honolulu 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		 96% n=120
Late December
16th–end		 93% n=128
Full month average 94% n=248
10.6 h median sunshine per day 86% of days exceed 8 h sunshine 27% of days see ≥ 1 mm rain — rain is not hidden
Comparison (old vs new): WMO-code “clear” bar: 33%. Sunshine-based “warm & sunny”: 94%. The 61-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

Honolulu is mostly overcast in December historically: only 33% of days are clear across 8 years (n=248), avg high 79°F. Most visitors this month will see more clouds than sun.

Every month in Honolulu

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

Historical clear-sky % for Honolulu, all months, ERA5 2018–2025.
Month % Clear Sample (n)
January 36% n=248 All destinations →
February 24% n=226 All destinations →
March 22% n=248 All destinations →
April 14% n=240 All destinations →
May 21% n=248 All destinations →
June 30% n=240 All destinations →
July 20% n=248 All destinations →
August 31% n=248 All destinations →
September 24% n=240 All destinations →
October 24% n=248 All destinations →
November 26% n=240 All destinations →
December ← this page 33% n=248 All destinations →

Frequently asked

Does it rain in Honolulu in December?

Sometimes. Honolulu sees measurable rain on 27% of days in December historically (n=248 days, ERA5 2018–2025) — not frequent enough to plan around, but not negligible either.

Is Honolulu good for sun in December?

It's mixed. Honolulu in December is clear on 33% of days historically (avg high 79°F, n=248 days, ERA5 2018–2025) — the outcome varies year to year.

How Honolulu compares in December

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