ERA5 almanac — 8 years of real data

Honolulu in January

Honolulu in January: 26% of days see measurable rain, 78°F average high, 36% of days historically clear (n=248, ERA5 2018–2025).

Honolulu in January is historically a poor month for sun: only 36% of days clear across 8 years (n=248, avg high 78°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 January

Clear-sky percentage for Honolulu in January, split by half-month. “n” is the number of days sampled across 8 years (2018–2025).
Period	% Clear days	Sample (n)	Avg high
Early January 1st–15th	38%	n=120	78°F
Late January 16th–end	35%	n=128	78°F
Full month average	36%	n=248	78°F

Sunshine & warmth in January

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 January. Primary: % of days ≥ 72°F with > 6 h of sunshine.
Period	Warm & sunny (≥72°F, >6 h sun)	Sample (n)
Early January 1st–15th	94%	n=120
Late January 16th–end	95%	n=128
Full month average	95%	n=248

10.7 h median sunshine per day 90% of days exceed 8 h sunshine 26% of days see ≥ 1 mm rain — rain is not hidden

Comparison (old vs new): WMO-code “clear” bar: 36%. Sunshine-based “warm & sunny”: 95%. The 59-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 January historically: only 36% of days are clear across 8 years (n=248), avg high 78°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 ← this page	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	33%	n=248	All destinations →

Frequently asked

Does it rain in Honolulu in January?

Sometimes. Honolulu sees measurable rain on 26% of days in January historically (n=248 days, ERA5 2018–2025) — not frequent enough to plan around, but not negligible either.

Is Honolulu good for sun in January?

It's mixed. Honolulu in January is clear on 36% of days historically (avg high 78°F, n=248 days, ERA5 2018–2025) — the outcome varies year to year.

How Honolulu compares in January

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.

→ Honolulu vs Lanai in January — Lanai is 32% clear historically
→ Honolulu vs Maui in January — Maui is 25% clear historically

→ Honolulu live forecast — this week’s actual 7-day weather, not historical
→ Best destinations in January — all destinations ranked by January clear-sky %
→ All destinations
→ Raw data (JSON) — buckets, n, source

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.