Best Time to Visit Chiang Rai
Recommended: Nov to Feb
When to go
November to February is coolest and driest, best for temple visits and hill views. March and April bring burning season: farmers clear fields and haze can blanket the north, cutting visibility and irritating lungs, same problem as Chiang Mai. May to October is hot and wet but temples and museums are mostly indoor or covered anyway.
Month by month in Thailand
Chiang Rai 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.