Best Time to Visit Chiang Mai
Recommended: Nov to Jan
When to go
November through January: cool, dry, clear mountain views, and Yi Peng lantern festival in November. Avoid February to April, burning season, when agricultural and forest fires push PM2.5 into hazardous territory and Chiang Mai regularly ranks among the world's most polluted cities, worst in March. May to October is hot and wet but green and cheap.
Month by month in Thailand
Chiang Mai sits in Thailand, so the country's broader seasonal pattern applies. November to February is dry and cool almost everywhere and the closest thing to a universal answer. After that it splits by coast: the Andaman side and the Gulf side flood at different times of year.
Nov-FebCool and dry nationwide, the safest bet for Bangkok, Chiang Mai and both coasts. Also the most crowded and priciest.
Mar-AprHot season, temperatures spike into the high 30s. Songkran water festival mid-April is chaotic fun if you don't mind getting soaked.
May-OctSouthwest monsoon soaks the Andaman coast (Phuket, Krabi), wettest around Sept. The Gulf side (Koh Samui) stays comparatively dry through most of this window.
Oct-DecNortheast monsoon flips it: Koh Samui and the Gulf islands get their rain, peaking in November, while the Andaman coast dries out.