Chiang Mai burning season runs from late January to mid-April, with March being the worst month. In 2024 Chiang Mai was ranked the most polluted city in the world multiple times during March with AQI readings exceeding 300+. The smoke comes from agricultural burning (crop clearing) and forest fires in northern Thailand, Myanmar, and Laos. This guide covers the month-by-month timeline, AQI scale explained, essential survival tips (N95 masks, air purifiers, IQAir app), best indoor activities (cooking classes, massage, coworking, museums), escape routes to southern Thailand, and whether you should visit during burning season. February is moderate, March is worst, late April improves with first rains.