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.

Gulf of Thailand · Seasons & weather

Best time to visit Khanom

Khanom runs on the southern Gulf calendar: dry from February to September, wet from October to December. It is the opposite of Phuket, and it catches people out.

The southern Gulf is upside down

Khanom faces Koh Samui across a narrow strait and shares its weather, which is not the weather most people picture when they think of Thailand. The rain here comes with the north-east monsoon from roughly October to December, not with the south-west monsoon that soaks Phuket from May to October.

So the months that are hopeless on the Andaman coast — June, July, August — are some of the best in Khanom, and the November you booked because it is high season in Phuket is the wettest month of the year here. If you are combining coasts on one trip, this is the single most useful thing to know.

Transport

Tickets & connections

Search tickets on 12go

In short

Khanom seasons

February–April: driest, hottest, clearest water
May–September: mostly dry, short showers, low prices
October–December: the rainy season, November and December worst
Pink dolphin trips: most reliable February to September
Same calendar as Koh Samui, the opposite of Phuket

February to September, the long good season

February to April is the driest and hottest stretch, with clear water and very little wind. May to September stays largely dry on this coast, with short showers rather than settled rain, and it has the advantage of being the European summer holiday without European summer prices.

This is also the reliable window for the pink dolphins in the bay north of town. The animals are resident year round, but the small boats only go out when the sea is flat, and the sea is flat far more often between February and September.

Good to know

Planning around the weather

Do not use Phuket's season to plan Khanom — they are on opposite calendars.
Dolphin boats depend on a flat sea, not on the month printed in a brochure.
November and December can flood the coast road; leave slack in your travel plans.
Donsak pier, the crossing to Koh Samui, is half an hour away and runs all year.

October to December: the wet end

The rain builds through October and peaks in November and December, when the north-east monsoon runs straight onto this coast. It rains hard and for long stretches, roads flood locally, and the sea is too rough for boat trips. Some smaller places close for a few weeks.

January is the recovery month: still showery at the start, drying out by the end, cheap and very quiet. If you want Khanom almost to yourself and do not mind gambling on a few grey days, late January is the value pick of the year.

Month by month

January	Showery at first, drying out and very quiet
February	Dry, calm and clear — the season starts properly
March	Hot and dry, the clearest water of the year
April	Hottest month, Songkran mid-month, still dry
May	Hot with brief showers, low prices
June	Warm and mostly dry — excellent value
July	Warm, short showers, quiet beaches
August	Warm and largely dry, the European summer pick
September	Still good, showers slowly increasing
October	The rains arrive, sea getting rough
November	Wettest month — heavy rain, no boat trips
December	Wet and windy, improving towards New Year

Frequently asked questions

When is the best time to visit Khanom?

February to September. February to April is the driest and clearest, while June to September is quiet, largely dry and much cheaper than the same months on the Andaman coast.

When is the rainy season in Khanom?

October to December, with November and December the heaviest. This is the north-east monsoon, the same season that soaks Koh Samui.

When can you see the pink dolphins at Khanom?

They live in the bay all year, but the boats need a calm sea. February to September is when trips run most reliably.

Is Khanom's weather the same as Phuket's?

No — it is close to the opposite. Phuket is wet from May to October; Khanom is dry through most of those months and wet from October to December.

Travel guides

More guides to Khanom and the southern Gulf coast.

Part of the guides for

Khanom

Khanom