Best Time to Visit Koh Samui

An island on the other monsoon

Koh Samui sits in the Gulf of Thailand, and its weather runs roughly opposite to the Andaman coast. While Phuket is at its wettest from May to October, Samui stays mostly dry — its rainy season is short and late, concentrated in October, November and December when the north-east monsoon blows in off the sea.

That flip is the key to planning. The classic dry season from January to April brings calm seas and day after day of sun, while June to August — peak holiday time in Europe — is a warm, mostly dry shoulder season with brief showers and lower prices. It is one of the few Thai islands where a summer trip is a genuinely good idea.

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At a glance

Driest, sunniest months: January–April
Rainiest stretch: October–December
Hottest months: March–May, often 33°C+
Samui's monsoon runs opposite to Phuket's — rain comes late

Good to know

Book January–April beachfront rooms well ahead — it is the island's proper high season.
Ang Thong marine park trips are best in the dry months, when seas are calm and visibility at its best.
In the October–December rains, keep ferry and flight plans flexible — crossings do get cancelled.
Sunset is a west-coast affair: Lipa Noi and Nathon put on the show while Chaweng faces the sunrise.

Dry season: January to April

These are Samui's postcard months: reliable sun, gentle seas and long golden evenings on the west coast at Lipa Noi. The island is at its busiest, so beachfront villas and the better restaurants fill — book ahead, especially around New Year and Easter.

March and April are the hottest, with afternoons above 33°C and the sea like a warm bath. It is prime time for boat trips to Ang Thong marine park, where the water is at its clearest and calmest.

Kayaks in the Ang Thong marine park near Koh Samui

Green season and the late rains

May to September is warm and largely dry, with short tropical showers that pass quickly. The island turns lush, the waterfalls at Na Muang actually have water, and you can find real bargains on rooms that cost twice as much in February.

October to December is the true wet season, with November usually the peak. Rain can set in for days at a time, seas turn rough, and boat trips get cancelled. It is the time for spa days and long lunches — or for going somewhere else and coming back when the sky clears.

Na Muang waterfall on Koh Samui in the green season

Month by month

January	Drying out, sunny spells return
February	Dry, calm and sunny — excellent
March	Hot and dry, clearest water
April	Hottest month — Songkran on the island
May	Hot, brief tropical showers
June	Warm and mostly dry — great value
July	Warm, short showers, lively but not packed
August	Warm, mostly dry, family season
September	Showers increasing slowly
October	Rainy season arrives
November	Often the wettest month — rough seas
December	Rainy early, improving towards New Year

Frequently asked questions

When is the rainy season on Koh Samui?

October to December, with November typically the wettest month. Unlike Thailand's west coast, Samui stays mostly dry through the European summer.

Is Koh Samui good in July and August?

Yes — June to August is a warm, mostly dry shoulder season on the Gulf. Expect brief showers, plenty of sun and better prices than the January–April peak.

When are the seas calmest around Samui?

Roughly January to September the Gulf is calm and good for swimming and boat trips. November and December can bring wind, rough seas and cancelled ferries.

Should I avoid Samui in November?

If beach weather is the whole point, yes — November is the riskiest month. If you are flexible, you may still catch bright spells between the rains, and the island is at its greenest and quietest.

Best time to visit Koh Samui

An island on the other monsoon

Tickets & connections

Tours & activities