ERA5 almanac — 8 years of real data

Lanai in January

Lanai in January: 31% of days see measurable rain, 75°F average high, 32% of days historically clear (n=248, ERA5 2018–2025).

Lanai in January is historically a poor month for sun: only 32% of days clear across 8 years (n=248, avg high 75°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 Lanai 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 Lanai 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	41%	n=120	75°F
Late January 16th–end	24%	n=128	75°F
Full month average	32%	n=248	75°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 Lanai 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	92%	n=120
Late January 16th–end	89%	n=128
Full month average	90%	n=248

10.8 h median sunshine per day 90% of days exceed 8 h sunshine 31% of days see ≥ 1 mm rain — rain is not hidden

Comparison (old vs new): WMO-code “clear” bar: 32%. Sunshine-based “warm & sunny”: 90%. The 58-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

Lanai is mostly overcast in January historically: only 32% of days are clear across 8 years (n=248), avg high 75°F. Most visitors this month will see more clouds than sun.

Every month in Lanai

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

Historical clear-sky % for Lanai, all months, ERA5 2018–2025.
Month	% Clear	Sample (n)
January ← this page	32%	n=248	All destinations →
February	19%	n=226	All destinations →
March	20%	n=248	All destinations →
April	14%	n=240	All destinations →
May	17%	n=248	All destinations →
June	20%	n=240	All destinations →
July	20%	n=248	All destinations →
August	26%	n=248	All destinations →
September	16%	n=240	All destinations →
October	20%	n=248	All destinations →
November	31%	n=240	All destinations →
December	27%	n=248	All destinations →

Frequently asked

Does it rain in Lanai in January?

Sometimes. Lanai sees measurable rain on 31% of days in January historically (n=248 days, ERA5 2018–2025) — not frequent enough to plan around, but not negligible either.

Is Lanai good for sun in January?

It's mixed. Lanai in January is clear on 32% of days historically (avg high 75°F, n=248 days, ERA5 2018–2025) — the outcome varies year to year.

How Lanai compares in January

Head-to-head clear-sky comparisons against destinations travelers plausibly weigh against Lanai this month — same passport tier, similar flight distance, both sides from the same 8-year ERA5 record.

→ Lanai vs Honolulu in January — Honolulu is 36% clear historically
→ Lanai vs Maui in January — Maui is 25% clear historically

→ Lanai 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.