Koh Samui in December: Weather, Holidays and What to Do

December is a month of two halves. In the first two weeks, the rainy season is clearly winding down, but Ang Thong National Park stays shut until the 15th. From mid-month it gets drier — just as Christmas and New Year kick off the most expensive, earliest-booked-out stretch of the whole year.

At a glance

Weather in December

With around 260mm of rainfall over roughly 12 rain days, December is noticeably drier than November, though not yet as settled as the high season from January onward. The first two weeks can still bring heavy showers and a somewhat rough sea, after which the weather usually calms down steadily. For why Koh Samui's Gulf side behaves so differently from the rest of Thailand during this period, see our article Koh Samui weather and the truth about the rainy season. If you're arriving in the first half of the month, it's worth packing light rain protection — by around mid-December most years barely need it.

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

Ang Thong National Park stays closed through 15 December 2026, reopening as normal from the 16th — if you're arriving in the first half of the month, plan that tour for after the 15th. Full background in our Ang Thong article.

For unsettled-weather days, a Thai cooking class works well — indoors, weather-independent, and a nice change of pace from the beach:

from 1,750 THBUnique Activity Thai cooking class 4 hours Koh Samui★★★★★4.88 from 52 reviews

When the evenings clear up, a romantic sunset boat tour is a lovely way to end the day — a popular choice in the run-up to Christmas:

from 2,150 THBRomantic sunset sailing boat tour - Coastline Koh Samui with Buffet★★★★★5.00 from 5 reviews

For beach days, the south coast (around Thong Krut) tends to calm down again towards the end of the month, while the northeast around Chaweng and Lamai can still see noticeable swell until mid-month. More ideas for wet weather in our Top 10 rainy day activities, from shopping malls and night markets to a relaxing Thai massage.

Festivals and events in December

Around the turn of the year, the Central Festival Samui shopping mall in Chaweng usually hosts an edition of the Central Samui International Balloon Festival, with giant inflatable figures and family entertainment — the exact date shifts from year to year, so check Central Samui's Facebook page shortly before you travel. More on this and other recurring events in our Top 10 events in Thailand.

Important for planning: Christmas and New Year rank among the most expensive and earliest-booked-out weeks of the whole year — this holds regardless of the tail end of the rainy season, so book flights and accommodation for this period well in advance — for typical price ranges across the year, see our article Cost of a holiday on Koh Samui.

Fruit in season

Soursop season continues through December (running to around February), while the smaller winter pineapple harvest wraps up. More in our Top 10 fruits in Thailand.

Frequently asked questions

Does it still rain a lot on Koh Samui in December?

Less than in November, but not yet as little as from January onward: around 260mm of rainfall over about 12 rain days, trending drier towards the end of the month.

Is December a good time to visit Koh Samui?

The second half, yes — the weather improves noticeably. That same window is also the most expensive and busiest because of Christmas and New Year. The first half is cheaper but still rainy-season changeable, and without Ang Thong National Park.

Is Ang Thong National Park open in December?

Only from 16 December 2026 onward. Through 15 December the park stays closed for the annual rough-sea closure.

Is Christmas and New Year expensive on Koh Samui?

Yes, it's among the most expensive and earliest-booked-out weeks of the entire year, regardless of the tail end of the rainy season. Book flights and accommodation early if you're travelling then.

The new year brings the settled high season starting in January; before that, see how the rains were still showing up in November. For the full-year overview, read The best time to visit Koh Samui.