At mid-afternoon Friday, "dangerous" readings were recorded at Chiang Mai City Hall (106), the Lampang Meteorological Station (159), and the Phrae station, which had a reading of 134.
Viewed from the steps to Doi Suthep, the city of Chiang Mai was barely visible through the haze Friday morning.
Dramatic satellite photos and charts from Nasa showed the cause and extent of the wildfires, which are set on purpose every year at this time, supposedly to prepare fields for a new crop when the rainy season begins, in April or May.