Note: Single-source report; awaiting corroboration.
Chiang Mai, in northern Thailand’s mountainous highlands, often experiences darkened skies during the dry season due to smoke from seasonal fires. A NASA satellite image captured on April 22, 2026, showed haze partially obscuring valleys and ridges, resulting from agricultural and forest fires set to burn crop debris or manage forests. Fire activity increases notably from February through April, peaking in March and subsiding by May as rains begin.
Research indicates that smoke from biomass burning comprises about 70% of fine particulate matter (PM2.5) in Chiang Mai’s air during April. Other sources of pollution include vehicles, power plants, industry, and charcoal used for cooking and heating. The region’s geography plays a significant role; surrounding mountains restrict airflow and create temperature inversions that trap pollutants and haze within valleys.
On the day the satellite image was taken, ground-based air quality sensors registered unhealthy and very unhealthy PM2.5 levels in Chiang Mai and nearby areas, according to the World Air Quality Index project. Prolonged exposure to such pollution may cause respiratory and cardiovascular problems. The haze has also harmed tourism; for example, tourist arrivals in Pai, a popular backpacker destination northwest of Chiang Mai, declined by 90% after extended haze periods.
Meteorologists from the ASEAN Specialised Meteorological Centre reported unusually warm and dry weather in the region, prompting a March 27 alert of a "high risk" for severe transboundary haze, the agency's highest alert level.