Is the air quality good in Chiang Mai?
As of March 26, 2026, at 9:40 PM PT, Chiang Mai, Thailand is experiencing very unhealthy air quality with an AQI exceeding 220, driven primarily by elevated PM2.5 concentrations.
These conditions can significantly increase the risk of respiratory illnesses, aggravate cardiovascular conditions, and reduce lung function, especially among children, the elderly, pregnant individuals, and those with pre-existing health issues (1).
Air quality is dynamic and, like the weather, can change frequently. Chiang Mai ranked as the most polluted major city in the world on Thursday night.
Click here for a real-time air quality map of Chiang Mai.
While today's conditions are poor, it is worth noting that Chiang Mai's average PM2.5 concentration in 2025 was 18.2 µg/m³, corresponding to a "moderate" AQI of 63 and 3.6 times the WHO annual guideline of 5 µg/m³.
Chiang Mai, Thailand, ranked as the most polluted major city globally, as of March 26, 2026, at 9:40 PM (PT). Source: IQAir.
When will air quality improve in Chiang Mai?
Air quality is forecasted to improve gradually into the weekend.
Hourly air quality forecast for Chiang Mai, Thailand, as of March 26, 2026, at 9:40 PM (PT). Source: IQAir.
Over the past 30 days, levels were mostly moderate, with a spike to very unhealthy levels today and a previous episode of poor air quality around March 4 due to the crop burning season (2).
Over the past 30 days, levels were mostly moderate, with a spike to very unhealthy today and a previous episode of poor air quality around March 4 due to crop burning season (2).
Daily air quality trends for Chiang Mai, Thailand over the past 30 days. Source: IQAir.
Air quality map of Chiang Mai, Thailand, as of March 26, 2026, at 9:40 PM (PT). Source: IQAir.
What is causing poor air quality in Chiang Mai?
Poor air quality in urban Thailand is primarily caused by a combination of human activities and environmental factors, with seasonal haze from biomass burning and agricultural fires being a major contributor (3).
Additional sources include traffic congestion, industrial emissions, and urban design factors that limit air circulation, while in northern regions such as Chiang Mai, topography and cross-border pollution further worsen conditions (4).
Outdoor pollution also significantly affects indoor air quality as particulate matter infiltrates buildings, especially in naturally ventilated homes, making exposure difficult to avoid.
Long-term exposure to PM2.5 is associated with serious health risks, including respiratory and cardiovascular diseases, underscoring the need for effective mitigation strategies and increased public awareness (5).
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How can I protect myself from poor air quality?
- Get a free air quality app for real-time air quality alerts and forecasts.
- Shut doors and windows and set the HVAC to recirculate mode.
- Contribute to your community’s outdoor air quality data.
- Stay indoors when air quality is poor; if you do need to go outdoors, wear a KN95/FFP2 mask.
- Run a high-performance air purifier to filter particles, gases, and other pollutants.
