Weather in Ubon Ratchathani in September

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

September ranks 8 of 12 in Ubon Ratchathani: past the worst of the year but short of December, which is the month to book if the dates are open.

Rain on 24 of the month's 30 days, 9 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 89% nothing dries, including you.

What the averages hide

Averages flatten a month, and this one hides a few things: 11 days top 30 °C — hot spells arrive, but they break; the day barely swings — 5.7 °C between the overnight low and the afternoon high. Across the twenty years measured, the hottest September day reached 32.6 °C and the coldest night fell to 19.8 °C, and the wettest single day dropped 185 mm — roughly 61% 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 558 mm against 132 mm in the driest. In a month this wet, even a tame spread is a lot of rain in absolute terms — the 301 mm average is a reasonable planning figure, not a promise.

Wind is light at 5.7 km/h, so the temperature on the page is close to the temperature on your skin, and humidity at 89% is the real story though — it is the number that decides how the day feels, not the 29.4 °C.

How September sits in the year

Temperatures hold steady either side: 29.3 °C in August, 29.4 here, 29.9 in October. Nothing about the timing within the month matters much. Rain is the thing that moves: October brings 12 days less of it, so pushing the dates later buys drier weather.

Daylight in September

Ubon Ratchathani sits close enough to the equator that daylight barely moves all year — 12.2 hours in September, against a range of just 1.8 hours across the whole calendar. Sunrise and sunset land at roughly the same time whenever you come.

An inland climate

Despite being inland, the year stays fairly even: 17.8 °C between the year's warmest afternoons and coldest nights.

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 Ubon Ratchathani versus nearby

If Ubon Ratchathani is one option among several, the nearby comparison is worth making. Siem Reap is close enough to be a coin toss — within a degree on temperature, 1 day more rain. Nakhon Ratchasima is close enough to be a coin toss — within a degree on temperature, the same number of rain days.

So: September is a compromise. December is 32 points better and is what Ubon Ratchathani 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 Ubon Ratchathani

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