Best Time to Visit Phuket
Recommended: Nov to Mar
When to go
November to March is dry season and the only time the Andaman Sea is reliably calm for swimming. December and January are peak, driest, and priciest. April is hot and humid before the rains start. May through October is wet season, with September and October the wettest months and the highest drowning risk on west coast beaches.
Month by month in Thailand
Phuket 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.