01The short answer
November to February is the most reliable window across most of the country: drier, cooler and the peak tourist season. March to May is very hot. June to October is the main rainy season for most regions.
The important nuance is that the two coasts differ. The Andaman side (Phuket, Krabi) is wettest roughly May to October. The Gulf side (Koh Samui, Koh Phangan) is wettest around October to December.
02Month by month
A rough guide to what each part of the year looks like:
- ✓November–February — best overall; cool, dry, busiest and priciest
- ✓March–May — very hot, especially inland; quieter and cheaper
- ✓April — Songkran, the Thai new year water festival; book well ahead
- ✓June–September — rain on the Andaman coast, often short heavy bursts
- ✓October–December — wettest on the Gulf coast including Koh Samui
03Rain is not a dealbreaker
Rainy season in Thailand usually means an intense downpour for an hour or two, not all-day drizzle. Plenty of people travel then deliberately for lower prices and far fewer crowds.
What it does affect is ferries and island hopping, which can be cancelled in rough weather. Build in flexibility if the islands are the main reason for your trip.
