← Weather & seasons in Thailand
On the thirty-year normal, Chiang Rai’s driest month is February (12.7 mm), wettest is August (372.9 mm), hottest is April (34.7°C mean daily maximum) and coolest is January (13.8°C mean daily minimum) — colder than Chiang Mai’s own January. For 2026, the province banned all open burning from 9 March to 10 May, a shorter and later window than Chiang Mai province’s 1 January–31 May ban the same year.
The season bands, honestly
Chiang Rai is often bundled with Chiang Mai as “the North,” but the measured normals and the two provinces’ own burning-ban decisions show real differences underneath the similarity.
| Window | Measured conditions | What that means here |
|---|---|---|
| Nov – Dec | Cool, dry, clear. | The best window: air is clean, heat has broken, and the province's 2026 burning ban has not started yet. |
| Jan | Coolest month (13.8°C mean daily minimum) — colder than Chiang Mai's January (15.7°C). | Still dry and clear. Golden Triangle boat trips and hill-country travel are at their best here. |
| Feb | Driest month (12.7 mm). | Air quality typically starts to degrade toward the end of the month, ahead of the province's own ban start. |
| Mar – 10 May | 2026 open-burning ban in force. | Governor Chuchip Phongchai's "Fresh Air Operation" bans all outdoor burning from 9 March to 10 May 2026 — a shorter window than Chiang Mai province's own 1 January–31 May ban the same year. |
| Apr | Hottest month (34.7°C mean daily maximum). | Falls inside the ban window, in the stretch regional haze reporting typically identifies as worst. Songkran (mid-April) falls here too. |
| Jun – Jul | Rain increasing. | Green season begins; fewer crowds, lower prices. |
| Aug | Wettest month (372.9 mm) — wetter than Chiang Mai's own peak (223.3 mm). | The rainiest stretch of the year by a wide margin. |
| Sep – Oct | Rain easing. | Shoulder season; improving weather, good value. |
All figures are 1991–2020 normals for WMO station 48303 (Chiang Rai). The “what that means here” column is our own reading against the burning-ban dates, not a separate data source.
The 2026 open-burning ban, and how it differs from Chiang Mai's
Chiang Rai’s governor, Chuchip Phongchai, launched the province’s 2026 “Fresh Air Operation” on 9 March, banning all outdoor burning through 10 May 2026 as part of the drive to reduce PM2.5 pollution. That is a materially different window from Chiang Mai province’s own 2026 ban, which ran the full 1 January to 31 May — five months against Chiang Rai’s roughly two. Two neighbouring provinces facing the same regional haze problem chose different start dates and different total durations for their own control measures, which is itself worth knowing if you are choosing between the two.
As with any province-wide ban, this is a control measure, not a guarantee of clean air for its duration, and enforcement cannot stop every fire, including ones with cross-border origins.
Why April is the month to plan around
April is Chiang Rai’s hottest month on the thirty-year normal, at a 34.7°C mean daily maximum — two degrees cooler than Chiang Mai’s own April peak of 36.7°C, but still the hottest month of Chiang Rai’s own year. It also falls inside the province’s open-burning ban window, in the stretch regional haze reporting consistently identifies as worst, and Songkran falls in the same month.
What we could not confirm
- A city-specific PM2.5 exceedance-day count for Chiang Rai. The Pollution Control Department's 2025 briefing gives regional figures for the North only, not a Chiang Rai city number.
- Any exceptions or penalty amounts written into the 2026 ban. The Chiang Rai Times report states the ban's dates and framing but not a penalty schedule or a registered-exception process of the kind Chiang Mai's province published.
- 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.
- The split between domestic and cross-border burning as a share of any year's haze in Chiang Rai specifically. Widely discussed, not officially quantified in any source we could open.
Frequently asked questions
January, on the numbers. It is the coolest month on the thirty-year normal — a 13.8°C daily-minimum mean, genuinely cold by Thai standards and colder than Chiang Mai's January (15.7°C) on the same dataset — and it sits before the province's open-burning ban and the haze season that follows it. December is close behind and slightly warmer.
No, and the difference is worth knowing if you're weighing the two provinces. For 2026, Chiang Rai's governor launched a province-wide open-burning ban running from 9 March to 10 May — about two months. Chiang Mai province's own 2026 ban, covered on our Chiang Mai page, ran the full 1 January to 31 May, five months. Both provinces are responding to the same regional haze problem, but they set different windows and different start dates for their own control measures.
Wetter, on every figure this site has checked. Chiang Rai's annual normal is 1,723.5 mm over 111.1 rain days, against Chiang Mai's 1,139.2 mm over 91.6 days — roughly 50% more rain a year. Chiang Rai's wettest month, August at 372.9 mm, is well above Chiang Mai's own wettest month (223.3 mm, also August). The two northern cities share a climate pattern, not identical numbers.
Yes — April is Chiang Rai's hottest month on the normal (34.7°C mean daily maximum) and it falls inside the province's 9 March–10 May 2026 ban window, in the period regional haze reporting typically identifies as worst. That is the same overlap this site has documented for Chiang Mai, though Chiang Rai's ban ends ten days into May rather than running to the end of the month.
Not in the source we checked. The Pollution Control Department's 2025 haze briefing reports 2024 PM2.5 exceedance days by region — North 129, against Bangkok and vicinity's 97 — but gives no city-level breakout for Chiang Rai specifically, so this page does not print a Chiang Rai-only figure.
Related guides
- Best time to visit Chiang Mai — the neighbouring province, same haze problem, different ban dates.
- Air quality in Thailand — the PM2.5 standard and what people actually do about the haze season.
- Compare Thai cities — the same normals for twelve stations, side by side.
- Chiang Mai vs Bangkok
- Chiang Rai — the city guide.
- Explore Thailand — the section this guide sits in.
Timed your visit. Now time the move.
If Chiang Rai is more than a trip, see what is actually listed here before the next burning season sets your calendar.
Sources & References
- WMO Climatological Standard Normals 1991–2020 — Thailand station data sheets (NCEI Accession 0253808), Chiang Rai station 48303: annual rainfall of 1,723.5 mm over 111.1 rain days, wettest month August (372.9 mm), driest month February (12.7 mm), hottest month April at a 34.7°C daily-maximum mean, coolest month January at a 13.8°C daily-minimum mean, annual sunshine 2,412.6 hours
- Chiang Rai Times — "Chiang Rai Governor Launches 'Fresh Air Operation' To Reduce PM2.5 Buildup" (published 10 March 2026): Governor Chuchip Phongchai launched the province's 2026 open-burning ban, stated as running "from now until May 10, 2026" (announced 9 March 2026), prohibiting all outdoor burning as part of the province's PM2.5 reduction drive; the article gives no specific penalty amounts or stated exceptions
- Pollution Control Department (Ministry of Natural Resources and Environment) — Air Quality Situation and Measures for Haze Prevention and Mitigation in 2025 briefing: Thailand's 24-hour ambient PM2.5 standard is 37.5 micrograms per cubic metre; days exceeding that standard in 2024 by region were North 129, Northeast 113, Central 101, Bangkok and vicinity 97, West 84 — the briefing gives no separate Chiang Rai city figure
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.
