A clear, sourced, month-by-month guide to Ubon Ratchathani's Isaan climate — the cool dry season, the hot season and the southwest-monsoon rainy season, how it lines up with the July Candle Festival and Mun/Mekong flood risk, the best months to come, and exactly what to pack.
Ubon Ratchathani is warm to hot year-round with three broad seasons: a cool, dry stretch from November to February (the best time to visit or move), a hot season from March to April peaking around Songkran, and a rainy southwest monsoon from roughly May to October, wettest in August. Long-term averages (1991-2021, compiled climate data) put annual rainfall at around 1,513mm, with January the driest month (≈5mm) and August the wettest (≈282mm). As an inland Isaan city on the Mun River near its Mekong confluence, sustained monsoon rain also drives the province's periodic flood risk. If you want the driest, most comfortable weather — for a visit, a border run to Chong Mek, or a move — aim for the cool season.
Ubon Ratchathani's best and driest window. Northeast-monsoon air keeps humidity and rainfall at their lowest all year — December and January each average only a handful of millimetres of rain — with warm days and noticeably cooler, drier evenings than the rest of the year. This is the most comfortable stretch for exploring Pha Taem, Sam Phan Bok and the Chong Mek border area, and the season most relocators choose to arrive and settle in.
Heat builds quickly through March and peaks in April, the warmest month, with daytime highs regularly touching the mid-30s°C and Songkran (Thai New Year) celebrated province-wide in mid-April. Rainfall is still modest in March before climbing sharply by late April as the southwest monsoon approaches; plan strenuous outdoor time for mornings and evenings.
The southwest monsoon brings Ubon Ratchathani's wettest stretch, peaking in August. As a landlocked Isaan province on the Mun River near its Mekong confluence, rainfall here runs heavier and lasts longer than in coastal Thailand — July through September each bring roughly 250–280mm of rain across 19-20 rainy days. The city's famous Candle Festival falls in mid-July, squarely inside this wet stretch, and sustained monsoon rain is also the trigger behind the Mun/Mekong flood risk covered in our flood-risk guide.
Long-term (1991-2021) daytime highs, overnight lows, monthly rainfall, rainy-day counts and average relative humidity, per compiled climate-station data. Figures are historical averages — individual years vary, and the monsoon months in particular swing from bright to stormy day to day.
| Month | High | Low | Rain | Rainy days | Humidity |
|---|---|---|---|---|---|
| January | 30° | 19° | 5 mm | 1 | 59% |
| February | 32° | 21° | 12 mm | 2 | 56% |
| March | 34° | 23° | 40 mm | 6 | 58% |
| April | 34° | 25° | 86 mm | 10 | 63% |
| May | 33° | 25° | 191 mm | 17 | 74% |
| June | 32° | 25° | 206 mm | 17 | 78% |
| July | 31° | 25° | 247 mm | 19 | 81% |
| August | 30° | 24° | 282 mm | 20 | 83% |
| September | 30° | 24° | 280 mm | 19 | 85% |
| October | 30° | 23° | 123 mm | 11 | 79% |
| November | 30° | 21° | 34 mm | 3 | 69% |
| December | 30° | 19° | 7 mm | 1 | 63% |
Temperatures in °C. "Rain" is the long-term monthly average total for Ubon Ratchathani, not a daily certainty — see the Thai Meteorological Department (TMD) for current forecasts.
For the most reliable weather, come between November and February: dry, sunny days, the lowest humidity of the year and noticeably cooler evenings. The trade-off is essentially none -- this is Ubon Ratchathani's easiest season all round, with only a modest seasonal bump in accommodation demand. March to April is hot and mostly dry, good if you handle heat well and want Songkran's festival energy, with May marking the monsoon's arrival. The May–October monsoon is the value window — lower rents and quieter sightseeing, in exchange for short daily downpours and, in low-lying riverside spots, some flood exposure. Many relocators deliberately arrive in the cool season to settle in comfortably, then experience their first rainy season once they know the area.
Ubon Ratchathani flood-risk guide → · Candle Festival & things to do →
| Season | What to bring |
|---|---|
| Cool dry season (Nov–Feb) | Light, breathable daywear plus a light layer for cooler evenings and strong air-conditioning indoors -- overnight lows can dip into the high teens °C in December and January. Sunscreen, hat and sunglasses year-round. |
| Hot season (Mar–Apr) | The lightest fabrics you own, high-SPF sunscreen, a refillable water bottle and a hat. Plan strenuous activity for mornings; expect to want air-con downtime midday. Bring a waterproof phone pouch if you're around for Songkran in mid-April. |
| Rainy season (May–Oct) | Everything for the heat plus a compact umbrella or packable rain jacket, quick-dry footwear and a dry bag for electronics -- especially useful if you're visiting for the mid-July Candle Festival. Showers tend to arrive as short, heavy afternoon or evening bursts rather than continuous all-day rain. |
November through February is Ubon Ratchathani's best window: the driest, least humid stretch of the year, with warm days, cooler evenings and the lowest rainfall -- January averages just 5mm of rain across a single rainy day. It's also the most comfortable season for exploring Pha Taem National Park, Sam Phan Bok and the Chong Mek border area. Many long-stayers deliberately arrive in this window to settle in before experiencing their first rainy season.
The rainy season runs roughly May to October with the southwest monsoon, peaking in August at around 282mm of rain across about 20 rainy days -- July and September run nearly as wet. As an inland Isaan city on the Mun River, rainfall here tends to be heavier and more sustained than in coastal Thailand, and the same monsoon drives the Mun/Mekong flood risk covered in our flood-risk guide.
Ubon Ratchathani is warm to hot year-round. Long-term averages put daytime highs around 34°C at the April peak, easing to roughly 29-30°C through the rainy season and cool season, while overnight lows can drop into the high teens °C in December and January -- genuinely cool by Thai standards. High humidity, regularly 80%+ during the monsoon, makes the wet-season heat feel stickier than the thermometer alone suggests.
Yes -- the festival's mid-July dates fall squarely inside the rainy season, when the province typically sees 200mm+ of rain that month across roughly 19 rainy days. The parades and celebrations proceed regardless, but count on short, heavy downpours rather than all-day rain, and pack accordingly if you're visiting specifically for the festival.
It can be. Ubon Ratchathani sits on the Mun River near its Mekong confluence, and sustained monsoon rainfall between June and October has caused notable flooding in low-lying riverside areas and parts of Warin Chamrap in 2019, 2022 and 2023. It's a real but localized risk rather than a citywide one -- see the flood-risk guide for which areas to avoid or check before signing a lease.
Pack light, breathable clothing whatever the month, plus high-SPF sunscreen, a hat and sunglasses. Add a light layer for cool-season evenings (overnight lows can reach the high teens °C in December-January), and for the rainy season (May-October) bring a compact umbrella or packable rain jacket, quick-dry shoes and a dry bag for electronics -- especially useful if your visit lines up with the mid-July Candle Festival.
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Whether you come for the cool-season comfort or the value of the rainy season, match the right area to how you want to live, then browse houses, townhouses and apartments there.
General climate information based on long-term averages; actual weather varies year to year — check a current TMD forecast before you travel. Hero photo by Kim Hort on Pexels.