Koh Samui Weather in May
Koh Samui in May averages 31°C (88°F) during the day and 28°C (82°F) at night. Keep in mind that quite a bit of rainfall is expected this month.
Rainfall in Koh Samui in May
Historically, the month has about 17 days of rain, averaging 126 mm (5 in) in total. Expect frequent rainfall this month, and not just light drizzle. When it rains, it tends to come down hard.
Temperature in Koh Samui in May
May in Koh Samui brings typical temperatures with highs around 31°C (88°F) and lows of 28°C (82°F). Indoor breaks or shaded spots can make the warmer part of the day much more comfortable. Nights are warm at 28°C (82°F), which can make sleeping uncomfortable. Keeping windows open or using a fan can help. A cold shower before bed is also a good way to cool down.
Sunshine in Koh Samui in May
With approximately 193 hours of sunshine, the days are filled with clear skies. It makes it a perfect month for being outside.
Average water temperature in May
At 29°C (84°F), the water is very warm — more like a heated pool than the sea. Great for those who like warm water, though some may find it less refreshing on a hot day.If you prefer dry days with pleasant temperatures, January and February typically offer the best circumstances. If you're seeking pleasant, dry and sunny weather somewhere else in the world, our weather planner can help you explore other options.
Check the conditions for any month of the year.
For a detailed overview over the year and the best time to visit Thailand, check out our Koh Samui's climate page.
Koh Samui Temperature in May
Min Temperature
28°C (82°F)
Max Temperature
31°C (88°F)
Water Temperature
29°C (84°F)
Chance of Rain
56%
Precipitation
126 mm (5 in)
Rainy days
17 days
Humidity
80%
Sunshine
193 hours
Percentage Sunshine
Daily Historical Temperatures
49-year average (1976-2025)
Based on our historical records, temperatures in Koh Samui typically stay consistent throughout May, with daily highs averaging around 31°C (88°F). Nights are warm, with lows around 27°C (81°F).
Average temperatures in May
Daily Historical Precipitation
49-year average (1976-2025)
Average daily rainfall for each day of the month based on long-term records.
Average precipitation in May
Historical weather for Koh Samui in May
Browse day-by-day weather records for Koh Samui spanning 51 years. Select any month and year to see actual temperatures, rainfall, and conditions recorded on each day.
Koh Samui historical weather extremes in May
The extremes listed below come from historical weather data collected in Koh Samui from 1982 through 2026.
- The hottest May day on record in Koh Samui reached 37°C (99°F) (May 11, 1983).
- On May 17, 2009, Koh Samui saw its coldest May day with temperatures maxing out at 28°C (82°F).
- Koh Samui registered its coldest May night on May 29, 2013, with temperatures dropping to 23°C (73°F).
Best Places in Thailand in May
Find out more about the weather in Thailand and which places have the best travel conditions in this month. See all of Thailand in May →
perfect weather
pleasant
tolerable
unpleasant
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What to Wear in Koh Samui in May
Warm temperatures in May make for comfortable sightseeing weather. Pack breathable fabrics like cotton shirts, knee-length shorts or skirts, and comfortable walking shoes. A thin long sleeve for indoor spaces is handy. Prepare for significant rainfall with proper waterproof clothing and shoes. The water temperature sits at about 29°C (84°F), making it perfect for swimming and water activities. Don't forget to pack your favorite swimwear and perhaps some snorkel gear. Don't forget sun protection, sunglasses, sunscreen, and a hat. These are all good ideas with this much sunshine.What To Do in Koh Samui in May
We rated the following activities from 1 (least suitable) to 10 (best) to do.
Check the conditions for any month of the year.
For a detailed overview over the year and the best time to visit Thailand, check out our Koh Samui's climate page.
Temperature Rainfall Sunshine Humidity Water Temp
See the full Koh Samui climate overview or explore weather in Thailand.
