← Weather & seasons in Thailand
On the thirty-year normal, Udon Thani’s driest month is December (5.8 mm) and its coolest is January (16.7°C mean daily minimum) — two different months, unlike Rayong or Surat Thani where the two coincide. Wettest is August (298.9 mm) and hottest is April (36.5°C mean daily maximum), the second-hottest peak of any station in our twelve-city comparison. Separately, the province's sugarcane harvest and burn season runs through the early months of the year — see the honest gap below on exact 2026 dates.
The season bands, honestly
Udon Thani doesn't split its driest and coolest records into one clean month the way some coastal stations do. The bands below are built from the four extreme months in the thirty-year normal, not a full monthly table.
| Window | Measured conditions | What that means here |
|---|---|---|
| Dec | Driest month (5.8 mm) — among the driest single months of any station in our twelve-city climate set. | A strong candidate for the best window, though not yet the coolest month. |
| Jan | Coolest month (16.7°C mean daily minimum). | Genuinely cool by Thai standards. Udon Thani's driest and coolest months fall in different months, unlike Rayong or Surat Thani. |
| Feb – Apr | Sugarcane harvest and burn season. | The Northeast's sugarcane harvest, and the field-burning that accompanies it in some areas, runs through this stretch — see the honest gap below on why we can't give exact 2026 dates for this province. |
| Apr | Hottest month (36.5°C mean daily maximum) — the second-hottest of twelve Thai stations checked, behind only Chiang Mai. | Falls at the tail of the burn-season window and ahead of Songkran, mid-month. |
| May – Jul | Rain building. | The wet season lengthens gradually rather than arriving all at once. |
| Aug | Wettest month (298.9 mm). | The peak of the rainy season. |
| Sep – Nov | Rain easing. | Shoulder season heading back toward the December dry spell. |
All figures are 1991–2020 normals for WMO station 48354 (Udon Thani). The “what that means here” column is our own reading against the region's sugarcane calendar, not a separate data source.
The Isaan burn season, and what we could and couldn't confirm about it
Chiang Mai and Chiang Rai provinces have both published named 2026 open-burning ban windows with exact start and end dates, which our guides to those provinces cite directly. We looked for the same thing for Udon Thani and could not find a province-specific 2026 order with named dates from an official source — that's a real gap, not an oversight, and it's stated here rather than papered over with a Chiang Mai-style date range that doesn't exist for this province.
What we can confirm: the national Cabinet's 2026 PM2.5 plan, approved 10 February 2026, explicitly names the Northeastern region — Udon Thani's region — as one of the country's designated risk areas, alongside Bangkok and vicinity, the North, Central and West. And the most recent harvest season this site could document in detail, the one covered in news reporting dated to early 2025, shows the shape of the problem locally: a mill in Udon Thani purchased over 410,000 tonnes of burned sugarcane — 43% of its total procurement, well above the mandatory 25% limit on charred cane — covering roughly 41,000 rai of burned farmland, before the Industry Ministry ordered the company to stop buying burned cane.
Sugarcane is harvested across Isaan from around December through April, and burning ahead of harvest (which speeds cutting but drives PM2.5) is the recurring flashpoint the 2025 dispute illustrates. If you are timing a visit or a move around clean air specifically, treat February–April as the higher-risk window here, the same way it is treated in the north — without the exact provincial order dates we can cite for Chiang Mai and Chiang Rai.
Why April is the month to plan around
April is Udon Thani’s hottest month on the thirty-year normal, at a 36.5°C mean daily maximum — hotter than Bangkok's own April peak (35.7°C) and behind only Chiang Mai (36.7°C) among the twelve stations in our climate comparison. It also falls at the tail end of the harvest-and-burn window described above, and Songkran (mid-April) lands in the same stretch.
What we could not confirm
- A province-specific 2026 open-burning ban order for Udon Thani, with named start and end dates, of the kind Chiang Mai and Chiang Rai have published. Not found from an official source in this run.
- A full monthly rainfall or temperature table beyond the four extreme months. The archive that would supply every other month could not be reached from this run.
- Sunshine-duration data. Udon Thani's WMO submission reported no sunshine series, so that column is simply absent rather than filled from another source.
- The exact road distance from Udon Thani to the Thai–Lao Friendship Bridge in Nong Khai. We confirmed the bridge's own facts from an official source but did not confirm a distance figure we were willing to print, so none is given.
Frequently asked questions
There isn't one clean answer, and that's worth saying plainly. December is the driest month on the normal (5.8 mm) but January is the coolest (16.7°C mean daily minimum) — the two records fall in different months here, unlike Rayong or Surat Thani where they coincide. Either month is a reasonable choice; December favours dry weather, January favours cooler air.
Over the full year, no — Udon Thani's annual normal (1,444.9 mm) is higher than Khon Kaen's (1,231.4 mm). But in their single driest months the two swap places: Khon Kaen's December normal of 5.1 mm is actually the lowest single-month figure of any station in our twelve-city climate set, edging out Udon Thani's own December (5.8 mm) for second place.
It's the nearest major Thai city with an international airport to the crossing, but the First Thai–Lao Friendship Bridge itself is in neighbouring Nong Khai province, not Udon Thani — it opened on 8 April 1994, runs 1,170 metres from Nong Khai across the Mekong to a point about 2 km from Vientiane, and carries two vehicle lanes, two pedestrian walkways and a single rail line. Udon Thani functions as the regional hub travellers fly into before making the onward trip to the bridge.
We could not confirm a province-specific 2026 ban order for Udon Thani of the kind Chiang Mai and Chiang Rai provinces have issued, with named start and end dates. What we can confirm: the national Cabinet's 2026 PM2.5 plan, approved 10 February 2026, names the Northeastern region as a designated risk area, and the most recent harvest season this site could document (2025) saw a real, documented conflict in Udon Thani over burned sugarcane — a local mill bought over 410,000 tonnes of burned cane, 43% of its total, against a 25% national limit, drawing an Industry Ministry order to stop.
Udon Thani, by three-tenths of a degree — 36.5°C against Khon Kaen's 36.2°C, both in April. Of the twelve Thai stations in our climate comparison, only Chiang Mai runs hotter at its own peak, at 36.7°C.
Related guides
- Air quality in Thailand — the PM2.5 standard and how the north's and northeast's burn seasons compare.
- Compare Thai cities — the same normals for twelve stations, side by side.
- Udon Thani air quality — what is tracked locally.
- Udon Thani — the city guide.
- Khon Kaen — the neighbouring Isaan hub.
- Explore Thailand — the section this guide sits in.
Timed your visit. Now time the move.
If Udon Thani is more than a trip, see what is actually listed here before the next burn season sets your calendar.
Sources & References
- WMO Climatological Standard Normals 1991–2020 — Thailand station data sheets (NCEI Accession 0253808), Udon Thani station 48354: annual rainfall of 1,444.9 mm over 95.5 rain days, wettest month August (298.9 mm), driest month December (5.8 mm), hottest month April at a 36.5°C daily-maximum mean, coolest month January at a 16.7°C daily-minimum mean; the station reported no sunshine-duration series
- Thai PBS — "ครม.เห็นชอบมาตรการรับมือไฟป่า หมอกควัน ฝุ่น PM 2.5 ปี 2569" (published 10 February 2026): the Cabinet approved 2026 measures controlling pollution sources across forest, agricultural and urban zones, naming the Northeastern region among the country's designated risk areas alongside Bangkok and vicinity, the North, Central and West; no province-specific ban dates are given in this national-level approval
- Nation Thailand — "Udon Thani sugarcane farmers respond to burn ban with protest threat" (reporting on the 2025 harvest season): the Thai Sugar Udon Thani mill purchased over 410,000 tonnes of burned sugarcane, 43% of total procurement, exceeding the mandatory 25% charred-cane limit; roughly 41,000 rai of farmland was burned and the Industry Ministry ordered the company to stop buying burned cane as part of the national PM2.5 response
Primary and official sources are cited above. Government rules, fees and procedures in Thailand change over time and vary by office; always confirm current requirements with the relevant authority before relying on them. BAANLYY never takes paid placement in editorial content.
