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SunnyDays

ERA5 almanac — 8 years of real data

Kauai in January

Kauai in January: 69% of days see measurable rain, 69°F average high, 5% of days historically clear (n=248, ERA5 2018–2025).

Kauai in January is historically a poor month for sun: only 5% of days clear across 8 years (n=248, avg high 69°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 Kauai 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 Kauai 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		 8% n=120 69°F
Late January
16th–end		 3% n=128 69°F
Full month average 5% n=248 69°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 Kauai 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		 32% n=120
Late January
16th–end		 30% n=128
Full month average 31% n=248
10.2 h median sunshine per day 87% of days exceed 8 h sunshine 69% of days see ≥ 1 mm rain — rain is not hidden
Comparison (old vs new): WMO-code “clear” bar: 5%. Sunshine-based “warm & sunny”: 31%. The 26-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

Kauai is a poor choice for sun in January: just 5% of days clear historically (n=248). The 8-year record is consistent — this is not a fluke bad stretch.

Every month in Kauai

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

Historical clear-sky % for Kauai, all months, ERA5 2018–2025.
Month % Clear Sample (n)
January ← this page 5% n=248 All destinations →
February 2% n=226 All destinations →
March 2% n=248 All destinations →
April 1% n=240 All destinations →
May 0% n=248 All destinations →
June 2% n=240 All destinations →
July 0% n=248 All destinations →
August 0% n=248 All destinations →
September 0% n=240 All destinations →
October 1% n=248 All destinations →
November 2% n=240 All destinations →
December 4% n=248 All destinations →

Frequently asked

Does it rain in Kauai in January?

Yes, frequently. In Kauai, 69% of days in January 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 Kauai good for sun in January?

Not usually. Kauai is historically overcast in January: only 5% of days are clear (avg high 69°F, n=248 days, ERA5 2018–2025).

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.