The Smoky Season
You may have heard about it: the Smoke Season or Smoky Season. This is the time when the air in Chiang Mai is filled — too filled — with PM2.5 particles. It usually happens from late February until sometime in April when the rains start and wash the air clean and fresh again.
The problem arises at the end of the dry season, caused by forest fires here and there combined with farmers burning their crop waste, and other farmers setting fire to the bush because it allows them to harvest very special and valuable mushrooms. All of this happens over a large area, crossing borders.
The nuance is, 20 years ago nobody really talked about it. You’d come to Chiang Mai for a few days and maybe think, “Meh, it’s a bit hazy today.” If no one told you about the PM2.5 levels, you’d probably just ignore it. That’s also what many Thais still think — that the PM2.5 problem is something tourists caused.
But if you live here and scroll through Facebook in the morning, you’ll see posts showing the PM2.5 number, which is often too high, and then you think the air isn’t okay for the rest of the day. That said, 2025 was noticeably better than previous years, possibly because government efforts to reduce the fires are finally paying off.
If you want to keep an eye on it yourself, check out https://aqicn.org/map/chiang-mai/. If you’re sensitive to air quality or plan to stay longer, it might be better to avoid the city around March. If you’re flexible, check the link above to see if the air is good enough for a few days or adjust your route accordingly.
