Hazardously thick smog is blanketing 45 out of 77 provinces in the country, mostly in the North, with Chiang Mai suffering the worst levels of PM2.5 on Sunday.
The Geo-Informatics and Space Technology Development Agency reported at 1pm on Sunday that nine provinces were facing red (seriously harmful) levels of particulate matter 2.5 micrometres and less in diameter (PM2.5), ranging from 78.9 to 126.1 microgrammes per cubic metre of air over the past 24 hours. The safe threshold is at 37.5µg/m³.
The worst level was measured in the northern province of Chiang Mai, followed by 113.3 in Chiang Rai, 108.0 in Phayao, 104.5 in Nan, 104.0 in Mae Hong Son, 102.1 9in Lamphun, 95.0 in Lampang, 79.8 in Tak and 78.9 in in the northeastern province of Loei which is the only province in a red zone outside the North.
Orange (somewhat unsafe) levels of PM2.5 were detected in 36 other provinces, mostly in the Northeast. They ranged from 38.1 to 69.5µg/m³.
The provinces were, in descending order, Phrae, Bueng Kan, Sukhothai, Uttaradit, Nong Khai, Nong Bua Lam Phu, Amnat Charoen, Udon Thani, Kamphaeng Phet, Nakhon Phanom, Sakon Nakhon, Phitsanulok, Kanchanaburi, Chaiyaphum, Phetchabun, Ubon Ratchathani, Nakhon Ratchasima, Yasothon, Si Sa Ket, Uthai Thani, Kalasin, Buri Ram, Khon Kaen, Surin, Roi Et, Maha Sarakham, Mukdahan, Prachin Buri, Phetchaburi, Phichit, Nakhon Sawan, Suphanburi, Ang Thong, Prachuap Khiri Khan, Sa Kaeo and Lop Buri.
Provinces in the lower Central Plain, a part of the East and the South, had moderate and good air quality. Samut Sakhon had the best air quality with 12.9µg/m³ of PM2.5, followed by Samut Prakan with 13.5µg/m³.
Swiss air quality technology company IQAir rated Chiang Mai as the major city with the world's worst air pollution at 2.10pm on Sunday.
Chiang Mai governor Nirat Pongsitthaworn attributed the problem in Chiang Mai to spreading wildfires. He said the province needed reinforcements of firefighters.
The map from Gistda shows unsafe levels of smog in the North, the Northeast and parts of the Central Plain and the East.