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SunnyDays

ERA5 almanac — 8 years of real data

Maui in December

Maui in December: 40% of days see measurable rain, 74°F average high, 30% of days historically clear (n=248, ERA5 2018–2025).

Maui in December is historically a poor month for sun: only 30% of days clear across 8 years (n=248, avg high 74°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 Maui 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 Maui 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		 31% n=120 74°F
Late December
16th–end		 29% n=128 74°F
Full month average 30% n=248 74°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 Maui 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		 87% n=120
Late December
16th–end		 73% n=128
Full month average 80% n=248
10.4 h median sunshine per day 84% of days exceed 8 h sunshine 40% of days see ≥ 1 mm rain — rain is not hidden
Comparison (old vs new): WMO-code “clear” bar: 30%. Sunshine-based “warm & sunny”: 80%. The 50-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

Maui is mostly overcast in December historically: only 30% of days are clear across 8 years (n=248), avg high 74°F. Most visitors this month will see more clouds than sun.

Every month in Maui

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

Historical clear-sky % for Maui, all months, ERA5 2018–2025.
Month % Clear Sample (n)
January 25% n=248 All destinations →
February 16% n=226 All destinations →
March 15% n=248 All destinations →
April 19% n=240 All destinations →
May 26% n=248 All destinations →
June 40% n=240 All destinations →
July 33% n=248 All destinations →
August 43% n=248 All destinations →
September 34% n=240 All destinations →
October 28% n=248 All destinations →
November 30% n=240 All destinations →
December ← this page 30% n=248 All destinations →

Frequently asked

Does it rain in Maui in December?

Sometimes. Maui sees measurable rain on 40% of days in December historically (n=248 days, ERA5 2018–2025) — not frequent enough to plan around, but not negligible either.

Is Maui good for sun in December?

It's mixed. Maui in December is clear on 30% of days historically (avg high 74°F, n=248 days, ERA5 2018–2025) — the outcome varies year to year.

How Maui compares in December

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