Koh Samui weather in May
Temperature, sea and sunshine in May: long-term averages from 30 years of weather data, not a forecast.
Holiday weather in May
Good
Best time to visit: January – April
What is the weather like in Koh Samui in May?
In May, Koh Samui is hot: daytime highs average 30 °C, and even at night it stays warm at around 28 °C. The sea averages 30.5 °C – almost as warm as a bath. The sun shines for around 7 hours a day. It is the rainy season: rain falls on about 24 days, totalling 143 mm. On about 16 days the thermometer climbs to 30 °C or more. The air is often humid and muggy. All in all, May is a good month for a holiday in Koh Samui.
May compared
How the weather changes from April to June. Tap a month to open it.
More details for May
- Daylight
- 12 h 33 min06:00 – 18:33
- UV index
- 13 · extremeclear sky, noon (estimate)All months
- Muggy days
- 31 daysdew point 18 °C or more
- Wind
- 14 km/haverage daily peak
- Cloud cover
- 82 %on average
- Hot days
- 16 days30 °C or more
- Time zone
- UTC+7Asia/Bangkok
How the score comes together
- Temperatureweight 35 %100 %
- Seaweight 25 %100 %
- Sunshineweight 20 %60 %
- Few rainy daysweight 20 %0 %
Each factor is rated from 0 to 100 % and weighted for the travel style “Sun, sea & sand”.
What to pack in May
- Swimwear
- Sunscreen
- Sunglasses & sun hat
- Light, breathable clothes
- Water bottle – drink plenty
- Insect repellent
- Rain jacket or umbrella
Koh Samui in May: quick answers
Is Koh Samui hot in May?
Yes. In May, Koh Samui is hot: daytime highs average 30 °C and nights stay around 28 °C. On about 16 days the thermometer climbs to 30 °C or more.
Can you swim in Koh Samui in May?
Yes. In May the sea averages 30.5 °C – almost as warm as a bath.
Does it rain much in Koh Samui in May?
It rains often – on about 24 days, adding up to 143 mm.
Koh Samui month by month
The whole year in Koh SamuiAll destinations: ThailandWhere to go in MaySea temperature in May
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)