Thailand doesn't have one rainy season; it has two, on opposite schedules. Get the coast right and almost any month can be a good month.
Thailand's islands sit on two coasts with mirror-image weather. The Andaman coast (Phuket, Krabi, Koh Lanta, Khao Lak) takes the southwest monsoon roughly May–October and is dry and settled roughly November–April. The Gulf coast (Koh Samui, Koh Phangan, Koh Tao) runs later: its driest stretch is roughly February–April (Jan–Aug is broadly workable), and its wettest weeks come with the northeast monsoon in October–December, typically peaking in November. So when Phuket is at its stormiest in September, Samui is often having a fine late-green-season week — and when Samui is soaked in November, Phuket's high season is opening. Pick the month first, then the coast.
Everywhere in Thailand, "rainy season" mostly means energetic afternoon or overnight bursts rather than all-day grey — but the peak monsoon weeks on each coast can bring genuinely sustained rain and, on the Andaman side, rough seas with red-flag swimming days. Treat the table below as climatology, not a forecast: any single week can defy it.
| Month | Gulf coast (Koh Samui) | Andaman coast (Phuket) |
|---|---|---|
| January | Drying out fast, pleasant; sea calming | Peak season — dry, calm, busiest and priciest |
| February | Excellent — dry, settled | Excellent — dry, settled |
| March | Excellent; heating up | Excellent; heating up |
| April | Hot and mostly dry; Songkran mid-month | Hot; season winding down late month; Songkran mid-month |
| May | Warm, occasional storms — good value | Southwest monsoon begins; showers, surf building |
| June | Largely fine, brief showers | Wet-season rhythm; sunny spells between bursts |
| July | Largely fine; breezy | Wet; watch red flags for swimming |
| August | Good, with short storms | Wet; green-season discounts deepen |
| September | Showers increasing late month | Statistically the wettest stretch begins |
| October | Wet season arriving | Very wet early, often improving late month |
| November | Typically the wettest month | Drying out; season reopening |
| December | Wet early, usually clearing for the holidays | High season — superb; peak holiday pricing |
Broad climatological patterns as of mid-2026 — individual years vary meaningfully. Peak pricing on both coasts centres on mid-December to early January and Chinese New Year.
The best villa value in Thailand lives in the shoulder months: May–June and September on the Gulf side, late October–November and late April on the Andaman side. Owners discount meaningfully, the islands empty out, and the weather is usually far better than the word "monsoon" suggests. Booking direct sharpens this further — an owner can quote a green-season or long-stay rate on the spot in a way a platform's calendar never will; see how direct booking works.
Where to point the trip once you've picked the month: our Koh Samui and Phuket area guides.
Now pick the house. The collection is owner-direct, visited and vouched for — starting with Sandalwood on Koh Samui.
Browse the collection Traveler's guide to booking direct