Koh Samui in January: Weather, Season and What to Do

Is Koh Samui worth visiting in January? Yes, very much so: January is one of the most reliable months of the year — dry, sunny and calm seas. The trade-off is peak season pricing and bigger crowds than in the second half of the year, especially in the first week around New Year.

At a glance

Weather in January

The northeast monsoon that brings Koh Samui's rain from October to December noticeably eases off in January. With around 9 rain days and roughly 130mm of rainfall, the month is much drier than the year-end stretch, though not quite as bone-dry as February. What showers remain tend to be short, often overnight or early morning, with sunshine dominating the day. The east coast (Chaweng, Lamai) can still feel breezy in the first half of the month, while the west side around Nathon and Taling Ngam tends to stay calmer. For more on the mechanism behind this, see our article Koh Samui weather and the truth about the rainy season.

What you can do in January – and what you can't

Ang Thong National Park has been open as normal again since 16 December, after six weeks closed for rough seas — January is one of the best months for the trip, since the sea is usually at its calmest:

from 1,850 THBAngthong Marine Park Full-Day Speed Boat VIP Tour★★★★★4.72 from 389 reviews

A trip to the neighbouring islands is also well worth it now, since wind and swell rarely cause cancellations:

from 1,850 THBDay trip snorkeling Koh Tao & Koh Nang Yuan★★★★★4.78 from 169 reviews

Snorkelling visibility is usually already good in January, though it gets even better in February. For calmer beach days, Bophut and Maenam in the north often work better than the east coast. If a shower does get in the way, an air-conditioned island tour, a shopping mall or a night market are good backup plans — more ideas in our Top 10 rainy day activities.

A practical booking note: most boat tours pick you up between 7am and 8:30am so you're on the water before the midday heat builds. Sun cream, a hat and plenty of water still belong in your bag in January, since UV exposure this close to the equator is high even on a cloudy day. If you want to explore beyond the boat trips, the island's inland viewpoints are still pleasantly cool for a short hike in January, well before the heavier heat of April sets in.

Festivals and events in January

On 9 January 2027, Thailand marks Wan Dek, National Children's Day — on Koh Samui this is mostly visible at schools and in a few resorts with small programmes, rather than one island-wide event. The Full Moon Party on neighbouring Koh Phangan is calculated to fall on Friday, 22 January 2027, running as usual from around 21:00 to sunrise on Haad Rin Beach — dates follow the lunar calendar and can shift at short notice, so check closer to your trip.

Around New Year, it's also worth checking for the Central Samui International Balloon Festival at the Central Festival Samui mall in Chaweng, with giant inflatable figures and live music in the evening. The last confirmed edition ran from 30 December 2025 to 1 January 2026; whether there's another edition in early January 2027 had not been confirmed at the time of checking — worth a look at Central Samui's Facebook page before you travel. More on these and other dates in our Top 10 events in Thailand.

Fruit in season

Jackfruit is at its best in January — available year-round, but several sources note it's most fragrant between January and May. Cantaloupe melon is also at its main harvest now, running through March. If you prefer something creamy and tart, soursop is still in season until around February. More seasonal timings in our Top 10 fruits in Thailand.

Frequently asked questions

Does it rain a lot on Koh Samui in January?

No, relatively little: around 9 rain days and about 130mm of rainfall for the month, mostly in short showers overnight or early morning. Daytime stays mostly sunny and dry.

Is January a good time to visit Koh Samui?

Yes, climate-wise it's one of the most reliable months of the year. The catch is peak-season pricing and bigger crowds, especially in the first week around New Year — book the second half of the month if you want to avoid that.

Is Ang Thong National Park open in January?

Yes. The annual closure for rough seas ends on 15 December, and the park has run as normal since 16 December — January is actually one of the calmest and best months for the boat trip.

How warm is the sea on Koh Samui in January?

Around 28°C on average — comfortable for swimming and snorkelling, even though it's technically the slightly coolest month of the year.

See what comes next in February, the driest month of the year; before that, December saw the rainy season wind down. For the full-year overview, read The best time to visit Koh Samui, and for everything about the national park itself, see our Ang Thong article.