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SunnyDays

ERA5 almanac — 8 years of real data

Honolulu in April

Honolulu in April: 42% of days see measurable rain, 79°F average high, 14% of days historically clear (n=240, ERA5 2018–2025).

Honolulu in April is historically a poor month for sun: only 14% of days clear across 8 years (n=240, avg high 79°F). January is the clearest month for Honolulu historically. 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 April

Clear-sky percentage for Honolulu in April, split by half-month. “n” is the number of days sampled across 8 years (2018–2025).
Period % Clear days Sample (n) Avg high
Early April
1st–15th		 14% n=120 79°F
Late April
16th–end		 13% n=120 79°F
Full month average 14% n=240 79°F

Sunshine & warmth in April

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 April. Primary: % of days ≥ 72°F with > 6 h of sunshine.
Period Warm & sunny (≥72°F, >6 h sun) Sample (n)
Early April
1st–15th		 97% n=120
Late April
16th–end		 97% n=120
Full month average 97% n=240
12.2 h median sunshine per day 90% of days exceed 8 h sunshine 42% of days see ≥ 1 mm rain — rain is not hidden
Comparison (old vs new): WMO-code “clear” bar: 14%. Sunshine-based “warm & sunny”: 97%. The 83-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 a poor choice for sun in April: just 14% of days clear historically (n=240). January is the historically strongest month for sun here. The 8-year record is consistent — this is not a fluke bad stretch.

→ See all destinations in January — historically the best month for sun in Honolulu.

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 ← this page 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 April?

Sometimes. Honolulu sees measurable rain on 42% of days in April historically (n=240 days, ERA5 2018–2025) — not frequent enough to plan around, but not negligible either.

Is Honolulu good for sun in April?

Not usually. Honolulu is historically overcast in April: only 14% of days are clear (avg high 79°F, n=240 days, ERA5 2018–2025). January is historically far better for sun here.

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.