Best Time to Visit Koh Tao

An island that lives by the sea

Koh Tao is Thailand's diving island, so the question of when to visit is really a question about the water. Like the rest of the Gulf, its rain comes late: October to December is the wet, windy stretch, while the long run from January or February through September is mostly dry, warm and settled.

Sairee beach on Koh Tao with longtail boats

For divers and snorkellers, the calm months are the prize — flat seas, warm water and good visibility, with many regulars rating the late spring and summer months as the best of all. That means the European summer holidays land in genuinely good conditions here, which few first-time visitors to Thailand expect.

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At a glance

Best diving conditions: roughly March–September
Rainiest stretch: October–December
Hottest months: March–May, often 33°C+
Whale shark sightings are possible year-round — never guaranteed

Good to know

Doing a dive course in July or August? Book the school a few days ahead — summer is student season.
The Chumphon ferry is the classic route in; morning boats generally get the calmest water.
In monsoon season, don't book a tight same-day ferry-to-flight connection — leave a buffer night.
Nang Yuan's viewpoint is best before 10am, ahead of the day-trip boats from Samui.

The calm months: February to September

From late winter to the end of summer, Koh Tao is at its easygoing best: calm crossings from Chumphon, gentle bays and dive boats heading out morning and afternoon. Snorkelling straight off the beach at Shark Bay or around Nang Yuan is at its clearest in these settled months.

March to May brings the hottest days, with the sea warm as a bath; June to August adds the summer crowd of backpackers and dive students, so the better schools and beachfront rooms are worth booking a little ahead. September usually stays kind, with showers building slowly.

Monsoon months: October to December

The north-east monsoon reaches Koh Tao late in the year. November is usually the peak: heavy rain, strong wind and rough crossings that can cancel ferries for a day or two at a time. Dive schools keep teaching in sheltered bays when they can, but visibility drops and boat days get lost.

It is not a write-off — between the fronts come bright, quiet days with the island half-empty and prices soft. But if your trip is short and diving is the goal, aim for the calm months instead and leave November to the flexible.

Boats sheltering in Mae Haad bay, Koh Tao

Month by month

January	Settling down, sea calming
February	Dry and calm — diving season under way
March	Hot, flat seas, fine visibility
April	Hottest month — superb water
May	Hot and calm, occasional showers
June	Warm, settled — great diving
July	Warm, busy with dive students
August	Warm, mostly dry, lively
September	Still good, showers building
October	Rains arriving, sea picking up
November	Wettest month — rough crossings
December	Windy and showery, slowly improving

Frequently asked questions

When is the best time for diving on Koh Tao?

Roughly March to September, when seas are calm and visibility at its best. Diving runs year-round, but October to December brings wind, rain and reduced visibility.

When is the rainy season on Koh Tao?

October to December, peaking in November. Like the rest of the Gulf, Koh Tao stays largely dry through the European summer months.

Can ferries to Koh Tao be cancelled?

Yes — in the November–December monsoon, rough seas occasionally halt crossings from Chumphon and Surat Thani for a day or two. Build slack into travel plans in those months.

When can you see whale sharks at Koh Tao?

Sightings happen year-round and are never guaranteed. Many divers report clusters of sightings in the settled months around March–May and again around September–October.

Best time to visit Koh Tao

An island that lives by the sea

Tickets & connections

Tours & activities