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Decision guide · reviewed on 29 October 2026
Best time to visit Thailand: the right coast in the right month.
Bangkok, the north and the two coasts do not share the same calendar. The Tourism Authority of Thailand (TAT) describes the country under summer and winter monsoons: a rainier season, a cooler and drier winter, and a hotter summer. It does not treat the map as one month. The day-to-day forecast is confirmed with the Thai Meteorological Department (TMD).
The TAT Newsroom is more specific on the coasts: the southwest monsoon arrives mainly from May to October in the southwest, with September often the heaviest; Phuket and the Andaman coast feel that window. In the Gulf, Koh Samui, Koh Phangan and Koh Tao rain later — from October to December, peaking in November and easing in January. The two coasts are not interchangeable.
| Area | What official sources help you understand | How to read it for the trip |
|---|---|---|
| Bangkok and the north | The TAT describes the country with a rainier season, a cooler and drier winter and a hotter summer. Bangkok and Chiang Mai follow this general shape, not the Gulf calendar. | City, temples and, in the north, a slower pace. Confirm the month with the TMD: the drier “winter” does not start on the same day every year. |
| Andaman coast (Phuket, Krabi, Railay) | The TAT Newsroom marks the monsoon from May to October in the southwest, with Phuket more exposed to the Andaman Sea. Smaller islands may reduce operations in that window. The TAT describes November as favourable on this coast. | Beach, cliffs and boat trips. Outside the southwest monsoon, the sea is usually the argument; during the monsoon, leave slack and a plan B. |
| Gulf (Koh Samui, Koh Phangan, Koh Tao) | The same TAT Newsroom — and the Ko Samui page — place the useful rain on these islands from October to December, peaking in November. Do not copy Phuket’s calendar. | Beach with a different rhythm. In December you may still be in the tail of the rains; January is when the TAT describes the easing. |
Who each window and area is for
After the May-to-October monsoon in the southwest, the Andaman and the interior enter the simpler window for beach and city — with the caveat that the Gulf can still be wet in November and December. May to October is for anyone who accepts the monsoon in the southwest, or who favours the Gulf while the Andaman is less settled. No month is perfect in all three areas at once.
Do not mix Bangkok, Chiang Mai, Phuket and Koh Samui in one week. Twelve or fourteen nights are enough for city, north and one coast. With fewer nights, choose one coast. The destination guide helps split the stages; this page decides the month.
Planning example (not a package): in January, twelve nights with Bangkok, Chiang Mai and the Andaman coast. In November, the same shape, or the Gulf if you accept the tail of the rain in Samui. In August, one coast only — and check whether ferries and boat trips are running.
What should appear in the proposal
- Month, crossed with the coast (Andaman and Gulf do not share the same rain peak).
- Nights in Bangkok, in the north and at the beach — two poles work better than four in a short week.
- Domestic flights, ferries and transfers; the TAT warns that monsoon crossings need confirming on the day.
- Whether the beach is non-negotiable, and on which coast.
- Your preferred departure airport.
Frequently asked questions
What is the best time to visit Thailand?
It depends on the area. For Bangkok, the north and the Andaman, the simpler window is after the May-to-October monsoon the TAT describes in the southwest. Koh Samui rains later. There is no perfect month for the whole country.
December in Phuket or in Koh Samui?
It is not the same bet. Phuket is on the Andaman coast, whose monsoon the TAT places mainly through October. Koh Samui is in the Gulf, with rain from October to December and a November peak. Confirm the TMD forecast for your week.
Does the rainy season make Thailand unworkable?
Not automatically. It changes the pace and can delay ferries or boat trips. The TAT asks travellers to follow TMD warnings. Leave slack in the programme.
Do Bangkok and the north follow the same calendar as the beaches?
No. The TAT describes the country with three general seasons; the two coasts have staggered monsoons. A circuit has to serve the areas you will actually visit.
How many nights for city and beach?
Twelve nights cover Bangkok, a northern block and one coast without living in transfers. A short week asks for one city and one beach, not both coasts.
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Sources: TAT — climate and weather, TAT Newsroom — monsoon and coasts, TAT — Thailand in November, TAT — Ko Samui, Thai Meteorological Department. Travel advice: check your own government (for example the UK FCDO or the US State Department; Portuguese citizens can use the Portal das Comunidades).