When to go
Use the seasonal notes below as broad planning guidance. They are not a forecast or a measured climate dataset. Check the local meteorological service, transport operator and site opening calendar for your dates.
Use the seasonal notes below as broad planning guidance. They are not a forecast or a measured climate dataset. Check the local meteorological service, transport operator and site opening calendar for your dates.
Best months for what you actually want to do
- Andaman coast: Phuket, Krabi, Phi Phi — November to March is the calm-sea window — Phi Phi and the bay tours run at their best. The May-October southwest monsoon brings red-flag seas and some boat cancellations, not constant rain.
- Gulf coast: Koh Samui, Phangan, Tao — The Gulf runs on the opposite calendar: its driest, calmest stretch is June to September, while November-January takes the monsoon. The two coasts together cover all twelve months.
- Budget travel — The green season (May-October, Andaman) halves room rates and empties the beaches; ferry schedules thin and some island venues close for a few weeks in September.
Shoulder season strategy
March-April (hot season, before the monsoon) is the Andaman value window: fewest crowds, 33°C heat, and Songkran's nationwide water festival in mid-April. October is the transition month as the seas calm.
Book December-January Phuket and Krabi rooms months ahead — Chinese New Year and European winter holidays stack. In green season, keep boat-day plans flexible and confirm morning-of; most operators credit rain cancellations.
Put the window together with the ready-made itinerary, the daily budget breakdown and the full the Thai islands guide. For general trip-timing advice, see our itinerary planning guide.
FAQ
When is monsoon season on each coast?
The Andaman coast takes the southwest monsoon May-October; the Gulf coast takes its rains (and the tail of northeast monsoon winds) roughly September-December, worst in November. Between the two coasts, some island is always in season.
Is the green season a bad time?
No — expect 14–17 rain days a month, usually in afternoon bursts, with long clear stretches between. Rates halve, the islands breathe, and swimming is fine off west-coast beaches on calmer days.
What is Songkran and when is it?
The Thai New Year water festival, 13-15 April every year (fuller festivities run longer in Chiang Mai). Expect total public water warfare — protect electronics and enjoy it; it is the country's biggest party.