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 Samet: Season, Rain and Weekends

The island in the rain shadow

Koh Samet has an unusual advantage: it sits in a rain shadow and gets noticeably less rain than the mainland coast a few kilometres away. In practice that means a wet-season week here often works out far better than the same week further east on Koh Chang.

The pattern still follows the south-west monsoon, so November to February is the dry, cool, reliable stretch, March to May is hot, and May to October is the rainy season. The difference is one of degree: rain on Samet tends to be short and sharp, and full days of grey are rare.

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In short

Koh Samet seasons

November–February: dry, cool nights, the best months
March–May: hot and dry, Songkran mid-April
May–October: rainy season, but drier than most of Thailand
Midweek is far quieter and cheaper than weekends
The island sits in a rain shadow — showers are usually short

The best months, and the hottest

November to February is the island at its best: dry, breezy, warm days and nights cool enough to sleep with the windows open. This is also high season, so rooms are dearer and weekends need booking ahead.

March to May is properly hot, with April the peak of it and Songkran, the national water festival, in the middle of the month. The sea is warm and calm, the island is still dry, and prices sit below the December peak — a good trade if you can handle the heat.

Good to know

Planning around the weather

Travel midweek if you can — it changes the island more than the season does.
Thai public holidays fill Samet as completely as weekends do.
September and October are the wettest months, but even then rain tends to be brief.
Ferries from Ban Phe run all year; rough weather rarely stops them for long.

The weekend effect

Because Samet is the closest island beach to Bangkok, it fills with weekend visitors in a way no other Thai island does. From Friday afternoon to Sunday the ferries are full, Hat Sai Kaew is packed, prices rise, and the good rooms go early.

Midweek the same island is calm and cheap. If your dates are flexible at all, arrive on a Monday or Tuesday — it makes more difference to what Koh Samet feels like than the month you choose.

Month by month

January	Dry, cool nights, calm sea — the best month
February	Dry and warm, reliable, busy at weekends
March	Getting hot, still dry, quieter midweek
April	Hottest month, Songkran mid-month, busy
May	First rains, still mostly sunny, prices ease
June	Warm showers, green, quiet on weekdays
July	Rain in short bursts, plenty of sun between
August	Wetter, but rarely a full day of rain
September	Wettest month — and the emptiest
October	Rain easing, good value late in the month
November	Season turns, dry and fresh — very good value
December	Dry, cool and busy, prices climb to New Year

Frequently asked questions

When is the best time to visit Koh Samet?

November to February for dry, cool weather. If price matters more than perfect conditions, May and late October are good value and still mostly sunny.

Does it rain a lot on Koh Samet?

Less than most of Thailand. The island sits in a rain shadow, so even in the wet season the rain tends to come in short bursts rather than all day.

Is Koh Samet busy at weekends?

Very. It is the closest island beach to Bangkok, so Friday to Sunday it fills up and prices rise. Midweek it is a different, much calmer place.

Can you visit Koh Samet in the rainy season?

Yes, and it is one of the better Thai islands for it. Rooms are cheaper, the island is quiet, and full days of rain are uncommon.

Travel guides

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Koh Samet

Koh Samet

Best time to visit Koh Samet