Weather in Kota Kinabalu in September

A hard month. September is a hard month in Kota Kinabalu, and worth planning around. You should expect rain on 24 days of the month, which is more days wet than dry.

Kota Kinabalu barely has seasons. September scores 47 out of 100 against a best of 59 in February — a gap small enough that the month you choose matters far less here than the week you choose.

Rain on 24 of the month's 30 days, 8 of them heavy. At that frequency a wet-weather backup is not a contingency, it is the itinerary — book the indoor things first and treat the clear days as the bonus. Natural fibres and a second shirt for the day. At 85% nothing dries, including you.

What the averages hide

Averages flatten a month, and this one hides a few things: 16 days top 30 °C — hot spells arrive, but they break; the day barely swings — 4.3 °C between the overnight low and the afternoon high. Across the twenty years measured, the hottest September day reached 33 °C and the coldest night fell to 23.8 °C, and the wettest single day dropped 72 mm — roughly 26% of the month's rain in one day.

September is statistically steady but not small: the year-to-year variation is modest in relative terms, yet the wettest September on record still delivered 464 mm against 99 mm in the driest. In a month this wet, even a tame spread is a lot of rain in absolute terms — the 272 mm average is a reasonable planning figure, not a promise.

Wind is light at 5.5 km/h, so the temperature on the page is close to the temperature on your skin, and humidity at 85% is the real story though — it is the number that decides how the day feels, not the 30.1 °C.

How September sits in the year

Temperatures hold steady either side: 30.1 °C in August, 30.1 here, 30 in October. Nothing about the timing within the month matters much.

Daylight in September

Kota Kinabalu sits close enough to the equator that daylight barely moves all year — 12.2 hours in September, against a range of just 0.7 hours across the whole calendar. Sunrise and sunset land at roughly the same time whenever you come.

Sea temperature

The sea sits at about 29.6 °C in September — warm enough that the water offers no relief from the heat. The sea peaks at 30 °C in May and bottoms out at 27 °C — water lags the air by a month or two, which is why the best swimming often comes after the best weather.

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 Kota Kinabalu versus nearby

If Kota Kinabalu is one option among several, the nearby comparison is worth making. Sandakan is close enough to be a coin toss — within a degree on temperature, 4 days more rain. Zamboanga is a better bet in September — within a degree on temperature, 2 days more rain.

So: September works, with February the better month by 12 points if the dates can move. If they cannot, nothing here should stop you booking.

Every month in Kota Kinabalu

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