Weather in Hoi An in September

A hard month. September is a hard month in Hoi An, and worth planning around. You should expect rain on 22 days of the month, which is more days wet than dry.

September ranks 11 of 12 — near the bottom of Hoi An's year. February is the month that works, and the swing between the two is 44 points, which is a different holiday rather than a slightly better one.

Rain on 22 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 83% nothing dries, including you.

What the averages hide

Averages flatten a month, and this one hides a few things: 22 days top 30 °C, making the heat continuous rather than occasional; the day barely swings — 5 °C between the overnight low and the afternoon high. Across the twenty years measured, the hottest September day reached 35.7 °C and the coldest night fell to 23.8 °C, and the wettest single day dropped 214 mm — roughly 58% of the month's rain in one day.

September is moderately variable: 72 mm in the driest year against 1149 mm in the wettest, around an average of 371 mm. Roughly two Septembers in three land near that average, and the third does something else entirely.

Wind is light at 6.4 km/h, so the temperature on the page is close to the temperature on your skin, and humidity runs at 83%, high enough to notice on the warm days without dominating them.

How September sits in the year

Temperatures hold steady either side: 32.6 °C in August, 31.2 here, 29.2 in October. Nothing about the timing within the month matters much.

Daylight in September

Hoi An sits close enough to the equator that daylight barely moves all year — 12.2 hours in September, against a range of just 1.9 hours across the whole calendar. Sunrise and sunset land at roughly the same time whenever you come.

Sea temperature

The sea sits at about 29.5 °C in September — warm enough that the water offers no relief from the heat. The sea peaks at 29.9 °C in June and bottoms out at 24.1 °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

Off season. The genuine off season: cheapest by a distance, with the caveat that some tours and restaurants close entirely.

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

September in Hoi An versus nearby

If Hoi An is one option among several, the nearby comparison is worth making. Qui Nhon is close enough to be a coin toss — within a degree on temperature, 1 day more rain. Ubon Ratchathani is close enough to be a coin toss — within a degree on temperature, 2 days more rain.

So: September is a compromise. February is 41 points better and is what Hoi An is actually like at its best — worth moving the trip for if that is possible, and worth adjusting expectations for if it is not.

Every month in Hoi An

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