Most guides answer "when should I go to Thailand?" with November to February, and then stop. That is the safe answer, it is also the most crowded and most expensive one, and it throws away most of the year for no good reason.
The useful answer is a different question: which coast. Thailand has two of them, they are hit by different monsoons at different times, and once you know that, almost any month works.
Contents
The thing that surprises people
Thailand's west coast faces the Indian Ocean. Its east coast faces the Gulf of Thailand. They are perhaps 500 kilometres apart, and their wet seasons barely overlap.
| Coast | Islands | Driven by | Wet season |
|---|---|---|---|
| West — Andaman Sea | Phuket, Krabi, Koh Lanta, Phi Phi, Khao Lak | Southwest monsoon off the Indian Ocean | May – October, peaking in September |
| East — Gulf of Thailand | Koh Samui, Koh Phangan, Koh Tao | Northeast monsoon across the Gulf | October – December, peaking in November |
The Gulf islands sit sheltered from the southwest monsoon, which is why they stay comparatively dry through the exact months when Phuket is being hammered. When Phuket is under water, Samui is often in full sun — and in November it is the other way round.
Which coast, which month
| Months | Go here | Why |
|---|---|---|
| January – April | Either — Andaman at its best | Both coasts dry. Calm seas and clear water on the Andaman side, the best snorkelling of the year |
| May – September | Gulf of Thailand | The southwest monsoon is on the Andaman coast; Samui, Phangan and Tao are dry |
| October | The awkward month | The only month that can catch both coasts — see below |
| November – December | Andaman Sea | The Andaman coast has dried out; the Gulf is now in its wettest weeks |
October: the one awkward month
This is the detail that is missing from almost every Thailand guide, including the one this article replaces. The two wet seasons do not slot neatly together — they overlap by about a month.
The southwest monsoon is still finishing on the Andaman side while the northeast monsoon is already starting on the Gulf side. October is the one month where the "just switch coasts" trick does not reliably work. If your dates are fixed to October, plan for rain wherever you go — or head inland to Chiang Mai, which is drying out by then.
The three seasons, and what they cost
| Season | Months | Weather | Prices |
|---|---|---|---|
| 🌞 Cool and dry | November – February | Dry, comfortable, around 25–32 °C | Highest |
| 🔥 Hot and dry | March – May | Very hot, often 35 °C and above | Middling |
| 🌧️ Green season | June – October | Monsoon rain, humid, around 30–35 °C | Lowest |
Bangkok and the central plains follow the same rhythm as the Andaman coast but without the sea breeze. November to March is comfortable there; April and May push past 38 °C, which makes sustained sightseeing genuinely unpleasant rather than merely warm.
Mid-April is Songkran, the Thai New Year — three days of public holiday and the largest water fight in the world. It falls in the hottest part of the year, which is not a coincidence.
What rainy season actually looks like
"Rainy season" sounds like a write-off and mostly is not. The typical pattern is a heavy downpour in the afternoon or evening, an hour or two long, followed by clear skies. It is not weeks of drizzle.
- Prices drop sharply — accommodation in particular, and it is the same accommodation.
- The beaches are not crowded, and neither are the temples.
- The landscape is at its best: the jungle is green rather than dusty, and the waterfalls actually have water.
- The trade-off is the sea. On the Andaman coast during the southwest monsoon, waves can run several metres, boat trips get cancelled, and some beaches fly red flags. This is the real reason to switch coasts rather than tough it out.
Monsoon timings are climate patterns, not a timetable — they shift by a couple of weeks from year to year. Checked September 2026.
Now find the days off
You know which month. The planner works out which public holidays and bridge days turn the fewest days of leave into the longest trip — in your country.
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