When to go where: Thailand's weather, month by month.

The planner runs on this same two-monsoon map: it scores both coasts for your month, holds total transit to a ceiling set by your trip length (about 10 hours for a week away), and would rather drop a stop than rush you.

Travelling from the UK? We've mapped every school break to the right coast: Thailand on UK school holidays →

The system, in one minute

Thailand's weather runs on two monsoons. The southwest monsoon (roughly May–October) blows rain onto the Andaman coast — Phuket, Krabi, Khao Lak, Koh Lanta, Koh Lipe — and waters the North and the central plains. The northeast monsoon (roughly October–December) wraps around and dumps its rain on the Gulf coast — Koh Samui, Koh Phangan, Koh Tao — which sat protected all summer.

The result is a see-saw: the two island coasts are rarely wet at the same time. Add the North's own rhythm (gloriously cool November–February, smoky in the late spring burning season, lush and green in the summer rains) and you can build a great trip in any month — if you point it at the right regions.

Month by month: where's dry?

The three seasonal wrinkles worth planning around

Burning season in the North (roughly late February–April)

Agricultural burning across the region fills the northern valleys with smoke haze. Some years are mild, some are genuinely unhealthy — Chiang Mai has topped global air-pollution rankings on bad days. If your trip falls in this window and mountains were the draw, consider swapping north time for islands, or at minimum check live AQI before committing. This is the single most common seasonal mistake we see in Thailand itineraries, and almost no generic planner flags it.

Songkran (April 13–15)

Thai New Year is a nationwide water fight — three days of joyous, soaking chaos. It's either the best possible time to be in Chiang Mai or Bangkok, or your travel nightmare, depending entirely on your temperament. Either way: waterproof phone pouch, book rooms well ahead, and don't plan intercity travel on the 13th.

Full Moon and festival surges

Koh Phangan's Full Moon Party inflates ferry loads and room rates island-wide for several days each lunar cycle — check the date against your island-hopping window even if you're not going. Loy Krathong / Yi Peng (the November full moon) does the same to Chiang Mai, and it's worth it: the lantern release is one of the great sights in Asia.

Once your month has picked your coast, the route almost writes itself — our 14-night route comes in an Andaman version and a Gulf version for exactly this reason. And if the wet-side discounts are calling you, we wrote the honest case for answering: Thailand in the rainy season — the myth, the numbers, and the half-price math.

Tempted by the quiet parts of the map? We priced them in the days they take: what off-the-beaten-path Thailand costs.

One piece of paperwork is the same in every month: the Thailand Digital Arrival Card, filed in the 3 days before you arrive — free, about five minutes, and worth reading up on before a lookalike site charges you for it.