Thailand Air Quality Index (AQI)
Thailand's air quality varies dramatically by region and season. Bangkok struggles with urban smog year-round, while northern cities like Chiang Mai experience some of Asia's worst burning season pollution from February to April — with PM2.5 routinely 40–60× WHO guidelines. Thailand had 52,000 fire hotspots in 2023.
Most Polluted Cities
- Chiang MaiAQI 158
- Chiang RaiAQI 145
- BangkokAQI 112
Cleanest Cities
- PhuketAQI 52
- RayongAQI 95
- BangkokAQI 112
Central Thailand
Bangkok
Bangkok Metropolitan · Pop. 10.7M
Bangkok's 10 million vehicles and flat basin geography create persistent smog. The dry-season inversion (Nov–Apr) traps emissions under a temperature layer. In early 2023, Bangkok's AQI briefly hit 218 — hazardous — prompting emergency school closures. The BTS Skytrain expansion has helped, but vehicle growth outpaces it.
Northern Thailand
Chiang Mai
Chiang Mai · Pop. 1.3M
Chiang Mai regularly tops Southeast Asia's most-polluted city charts from February to April. Surrounded by mountains that trap smoke, the city receives smoke from agricultural field burning across northern Thailand, Myanmar, and Laos. The 2023 burning season pushed Chiang Mai's PM2.5 to 300+ μg/m³ for multiple days — nearly 60× WHO guidelines.
Chiang Rai
Chiang Rai · Pop. 250K
Thailand's northernmost major city sits at the Myanmar border. During burning season, smoke from Myanmar's vast agricultural fires combines with local burning, making Chiang Rai one of the most dangerous places for air quality in all of Asia during Feb–April.
Eastern Seaboard
Rayong
Rayong · Pop. 720K
Home to Map Ta Phut, one of Southeast Asia's largest industrial estates. Over 150 petrochemical and chemical plants operate in the area. Rayong has faced numerous environmental protests and lawsuits related to industrial pollution and cancer cluster concerns.
Southern Thailand
Phuket
Phuket · Pop. 420K
Thailand's premier tourism island has relatively good air quality compared to the north. Ocean winds from the Andaman Sea keep the island clean. A surge in development and tourism boats has slightly elevated PM2.5 in recent years, though it remains well below WHO annual guidelines in most months.
Chiang Mai Burning Season: Asia's Worst Haze
Every year from February to April, northern Thailand's mountain valleys fill with smoke from agricultural burning. Farmers in Thailand, Myanmar, and Laos burn crop residue and clear land — creating a regional haze that affects millions of people across three countries.
- 2023: Chiang Mai recorded PM2.5 of 306 μg/m³ on March 31 — 61× WHO's 24-hr guideline
- Schools and airports regularly close during peak haze events
- Tourism impact: Hotel cancellations spike 30–40% during severe haze months
- Transboundary issue: Up to 70% of Chiang Mai's burning-season PM2.5 originates outside Thailand
Traveler tip: Avoid Chiang Mai from late February to mid-April if you have respiratory conditions. Check the PCD (Pollution Control Department) app or IQAir for real-time readings before outdoor activities.
Thailand Air Quality by Season
Bangkok has moderate to unhealthy air due to inversion layers trapping vehicle emissions. North is cleaner before burning season starts.
Critical for northern Thailand. Chiang Mai and Chiang Rai can reach hazardous AQI 300+. Bangkok also deteriorates. Avoid outdoor exercise.
Rains clear the air across Thailand. Best air quality season. South (Phuket) gets its rainy season May–Oct. North dramatically improves.