Burning Season and Air Quality in Chiang Mai
Part of the Chiang Mai travel guide — see every topic in All Chiang Mai Guides.
Every year, from about February to April, smoke from farm burning and forest fires covers northern Thailand. In Chiang Mai the mountains disappear in the haze, and the air can be unhealthy for weeks. Plan around it.
When and how bad
The smoke usually builds in February, is worst in March and early April, and clears when the rains start in late April or May. In 2026, Chiang Mai's air quality index reached 263 on 29 March, with PM2.5 at 188 µg/m³ that morning, more than ten times the WHO daily guideline of 15 µg/m³. Some days are clear; others are very bad.
Why it happens
Farmers burn rice, maize and sugarcane fields before planting, and forest fires spread through the dry hills. Smoke also blows in from across the borders. Chiang Mai bans open burning for several months each dry season (in 2026, until 31 May), but the fires are hard to control: satellites counted more than 10,000 hotspots in the province by late April 2026.
Protect yourself
Check the air every morning on IQAir, Air4Thai (the official Thai app) or the DustBoy sensor map from Chiang Mai University. When the index is above 150, wear an N95 or KN95 mask outdoors; 7-Eleven sells them. Choose a hotel or condo with an air purifier and keep the windows closed. Exercise outdoors only on better days, early in the morning, and skip hikes on Doi Suthep and Doi Inthanon when the views are hidden.
Where to go instead
In March and April, go south to the sea: Krabi, Koh Lanta, Phuket and Koh Samui usually have clean air. Bangkok has its own smog season from about December to February but is usually better in March. Come to Chiang Mai from about June to January instead; November to January is cool, clear and the best time of the year.
Burning Season and Air Quality at a glance
| Season | About February to April; worst in March |
|---|---|
| 2026 peak | AQI 263 on 29 March; PM2.5 188 µg/m³ |
| WHO daily guideline | PM2.5 15 µg/m³ |
| Apps | IQAir, Air4Thai, DustBoy (Chiang Mai University) |
| Mask | N95 or KN95 when the AQI is above 150 |
| Escape to | Krabi, Koh Lanta, Phuket, Koh Samui |
| Best months | November to January |