Weather in Honolulu in September

A good month. September is a solid month to be in Honolulu. Highs average 28.6 °C, lows 25.6 °C, and rain falls on 12 days — nothing in the month is working against you.

Honolulu barely has seasons. September scores 72 out of 100 against a best of 81 in May — a gap small enough that the month you choose matters far less here than the week you choose.

Rain on 12 days, 1 of them heavy. Enough to need a plan B, not enough to need a plan around it. Pack for 28.6 °C days and 25.6 °C nights; the spread matters more here than any single number.

What the averages hide

Averages flatten a month, and this one hides a few things: the day barely swings — 3 °C between the overnight low and the afternoon high. Across the twenty years measured, the hottest September day reached 31 °C and the coldest night fell to 24 °C, and the wettest single day dropped 44 mm — roughly 88% of the month's rain in one day.

September is moderately variable: 5 mm in the driest year against 150 mm in the wettest, around an average of 50 mm. Roughly two Septembers in three land near that average, and the third does something else entirely.

Wind sits around 19.6 km/h — a steady breeze rather than a nuisance, and welcome on the warmer days, and humidity is unremarkable at 74%.

How September sits in the year

Temperatures hold steady either side: 28.5 °C in August, 28.6 here, 28 in October. Nothing about the timing within the month matters much.

Daylight in September

12.3 hours of daylight, losing 0.6 hours across the month. That is between Honolulu's extremes of 13.4 and 10.8 hours, so days are long enough not to constrain the plan.

Sea temperature

The sea sits at about 26.6 °C in September — warm enough to stay in as long as you like. This is the warmest the water gets all year.

How busy it gets

Quiet. Few other visitors, cheaper rooms, and a real chance some seasonal operators are shut.

Crowd levels are estimated from climate desirability and school-holiday calendars, not from visitor numbers.

September in Honolulu versus nearby

Honolulu has no close neighbour worth comparing against, so the useful question is how September there compares with September elsewhere. San Francisco in September is a clearly better month — 24.5 °C and rain on 1 days, against 28.6 °C and 12 here. San Jose in September is much the same — 31 °C and rain on 1 days, against 28.6 °C and 12 here.

So: September works, with May the better month by 9 points if the dates can move. If they cannot, nothing here should stop you booking.

Every month in Honolulu

See all twelve months in Honolulu, or where else to go in September.