Ko Samui weather in September
September is a fair month to visit Ko Samui: highs of 29°C (84°F) and about 181 mm (7.1 in) of rain on average. Nights average 27°C (81°F) and cloud cover 89% (NASA POWER, 2001–2025 averages). The sea averages 30°C (86°F). It is the 4th wettest month of the year and the 6th coolest. Compared with August, it is about as warm and wetter; October brings highs of 28°C (83°F) and 246 mm (9.7 in) of rain.
Is September a good time to visit Ko Samui?
fair month Weather score 52/100.
September is a fair month in Ko Samui. The weather is usually best in Feb–Apr.
Does it rain a lot in Ko Samui in September?
Yes, it is one of the rainy months: about 181 mm (7.1 in) falls in an average September. It is the 4th wettest month of the year.
How warm is Ko Samui in September?
Days average 29°C (84°F) and nights 27°C (81°F).
Ko Samui weather by month
| Month | High | Low | Rain | Cloud | Sea | Weather |
|---|---|---|---|---|---|---|
| January | 27°C (81°F) | 26°C (79°F) | 135 mm | 60% | 29°C (84°F) | fair |
| February | 28°C (82°F) | 26°C (79°F) | 38 mm | 46% | 29°C (85°F) | best |
| March | 29°C (84°F) | 27°C (81°F) | 114 mm | 49% | 30°C (86°F) | best |
| April | 30°C (86°F) | 28°C (83°F) | 90 mm | 65% | 32°C (89°F) | best |
| May | 30°C (86°F) | 28°C (83°F) | 170 mm | 86% | 32°C (90°F) | fair |
| June | 30°C (85°F) | 28°C (82°F) | 167 mm | 87% | 31°C (88°F) | fair |
| July | 29°C (84°F) | 28°C (82°F) | 166 mm | 89% | 31°C (87°F) | fair |
| August | 29°C (84°F) | 27°C (81°F) | 144 mm | 89% | 31°C (88°F) | fair |
| September | 29°C (84°F) | 27°C (81°F) | 181 mm | 89% | 30°C (86°F) | fair |
| October | 28°C (83°F) | 27°C (81°F) | 246 mm | 86% | 30°C (87°F) | least pleasant |
| November | 28°C (83°F) | 27°C (81°F) | 375 mm | 81% | 29°C (85°F) | least pleasant |
| December | 28°C (82°F) | 27°C (80°F) | 262 mm | 76% | 29°C (83°F) | least pleasant |
Sources: 2001–2025 monthly averages from NASA POWER (MERRA-2 reanalysis), sea temperature from Open-Meteo Marine. Page updated . How we rate months