Koh Samui weather in December
Temperature, sea and sunshine in December: long-term averages from 30 years of weather data, not a forecast.
Holiday weather in December
Good
Best time to visit: January – April
What is the weather like in Koh Samui in December?
In December, Koh Samui is hot: daytime highs average 28 °C, and even at night it stays warm at around 26 °C. The sea averages 27.9 °C – lovely and warm for swimming. Expect around 6 hours of sunshine a day. It is the rainy season: rain falls on about 17 days, totalling 165 mm. The air is often humid and muggy. All in all, December is a good month for a holiday in Koh Samui.
December compared
How the weather changes from November to January. Tap a month to open it.
| NovemberNov | DecemberDec | JanuaryJan | |
|---|---|---|---|
| Score | 66 | 71 | 83 |
| Day | 28° | 28° | 28° |
| Night | 26° | 26° | 26° |
| Sea | 29° | 28° | 28° |
| Sun | 5 h | 6 h | 7 h |
| Rain days | 24 | 17 | 10 |
More details for December
- Daylight
- 11 h 34 min06:28 – 18:02
- UV index
- 9 · very highclear sky, noon (estimate)All months
- Muggy days
- 31 daysdew point 18 °C or more
- Wind
- 17 km/haverage daily peak
- Cloud cover
- 71 %on average
- Hot days
- 0 days30 °C or more
- Time zone
- UTC+7Asia/Bangkok
How the score comes together
- Temperatureweight 35 %100 %
- Seaweight 25 %100 %
- Sunshineweight 20 %47 %
- Few rainy daysweight 20 %8 %
Each factor is rated from 0 to 100 % and weighted for the travel style “Sun, sea & sand”.
What to pack in December
- Swimwear
- Sunscreen
- Sunglasses & sun hat
- Light, breathable clothes
- Insect repellent
- Rain jacket or umbrella
Koh Samui in December: quick answers
Is Koh Samui hot in December?
Yes. In December, Koh Samui is hot: daytime highs average 28 °C and nights stay around 26 °C.
Can you swim in Koh Samui in December?
Yes. In December the sea averages 27.9 °C – lovely and warm for swimming.
Does it rain much in Koh Samui in December?
It rains often – on about 17 days, adding up to 165 mm.
Koh Samui month by month
The whole year in Koh SamuiAll destinations: ThailandWhere to go in DecemberSea temperature in December
Climate averages 1996–2025, not a forecast. Data: Copernicus ERA5 / ERA5-Land via Open-Meteo.com (CC BY 4.0), NOAA OISST, WMO 1991–2020 (NOAA NCEI), GeoNames (CC BY 4.0)