Thailand
Koh Samui weather by month
Koh Samui is warmest in May, with average highs of 33°C, and coolest in January at 29°C. The sea ranges from about 28°C to 31°C, warmest in May.
- WarmestMay33°C average high
- CoolestJanuary29°C average high
- Warmest seaMay31°C on average
- From Dublin≈ 13hdirect, estimated
Koh Samui through the year
Beach weather (highs of 25°C or more and fewer than seven rainy days) is most likely January to April. October is the wettest month, with rain on about 21 days.
Month by month
| Month | High | Low | Sea | Rainy days | Rain | Sky | Days 25°C+ |
|---|---|---|---|---|---|---|---|
| January | 29° | 24° | 28° | 6 | 126 mm | Often cloudy | 100% |
| February | 29° | 25° | 29° | 4 | 59 mm | Often cloudy | 100% |
| March | 31° | 26° | 29° | 4 | 118 mm | Often cloudy | 100% |
| April | 32° | 26° | 30° | 7 | 150 mm | Often cloudy | 100% |
| May | 33° | 26° | 31° | 12 | 150 mm | Mostly cloudy | 100% |
| June | 33° | 26° | 30° | 8 | 95 mm | Mostly cloudy | 100% |
| July | 33° | 25° | 30° | 9 | 106 mm | Mostly cloudy | 100% |
| August | 33° | 25° | 30° | 9 | 104 mm | Mostly cloudy | 100% |
| September | 32° | 25° | 30° | 14 | 179 mm | Mostly cloudy | 100% |
| October | 31° | 25° | 30° | 21 | 307 mm | Mostly cloudy | 100% |
| November | 30° | 24° | 29° | 19 | 371 mm | Mostly cloudy | 100% |
| December | 30° | 24° | 28° | 10 | 228 mm | Mostly cloudy | 100% |
Shaded rows: beach weather (January to April). Rainy days = days with 1 mm of rain or more, as weather stations count them. Sky = average cloud cover. How we measure
Flying time
Estimated from the distance for a direct flight. Real schedules vary, and many long-haul trips need a connection.
- From Dublin≈ 13h
- From Cork≈ 13h 15m
- From Belfast≈ 13h
- From London≈ 12h 30m
- From Manchester≈ 12h 45m
- From Glasgow≈ 12h 45m
Air: Copernicus ERA5-Land, 2011–2025, for the land nearest Koh Samui (8 m), matched to the official 1991-2020 averages for Koh Samui (WMO). Sea: Copernicus ERA5 sea surface temperature, 2022–2025. Averages describe past weather, not a forecast.