Ko Samui is rarely comfortable to be outside at midday. It comes closest in mid January, and even then it is too hot. For sun, aim for mid and late February.
When to go five ratings · thirty-six ten-day sections · click a cell to read it
The sun season here falls in mid and late February. It peaks in late January, at 59. The weakest stretch is from mid April to mid June, when it drops to 3, mostly because it is too hot. The clearest skies come in March, when the sky is typically 53% covered at midday (partly cloudy).
Being outside is not what Ko Samui is for: the Easy outdoors rating tops out at 5, mostly because it is too hot.
Walking is not what Ko Samui is for: the Active outdoors rating tops out at 0, mostly because it is too warm.
The year, measured
The average temperature in Ko Samui over the whole year is 29°C. May is the hottest month, with highs of about 32°C; December is the coldest, with lows of about 26°C. The rainy (wet) season in Ko Samui runs from October to December, peaking in November with a 76% chance of rain on a given day. The dry season is June to September; August is the driest month, at 46%. Winds in Ko Samui are highest in February, averaging 2.9 m/s (10 km/h), and lightest in October, at 1.4 m/s (5 km/h). The prevailing wind is from the SE. The clearest skies in Ko Samui come in March, when the sky is typically 53% covered; November is the cloudiest month, at 60%.
Month by month Ko Samui climate by month: average temperatures year round · click a month to read it
| Month | High | Low | Feels like | Chance of rain | Cloud | Wind | Being outside | Sun | Walking |
|---|---|---|---|---|---|---|---|---|---|
| January | 29°C | 26°C | 32°C | 57% | 57% | 2.5 m/s | 3 | 55 | 0 |
| February | 29°C | 27°C | 32°C | 61% | 55% | 2.9 m/s | 3 | 56 | 0 |
| March | 30°C | 27°C | 34°C | 56% | 53% | 2.4 m/s | 0 | 38 | 0 |
| April | 31°C | 28°C | 36°C | 62% | 54% | 1.9 m/s | 0 | 11 | 0 |
| May | 32°C | 28°C | 37°C | 63% | 56% | 1.6 m/s | 0 | 5 | 0 |
| June | 32°C | 28°C | 37°C | 56% | 57% | 1.6 m/s | 0 | 9 | 0 |
| July | 32°C | 27°C | 36°C | 53% | 58% | 1.6 m/s | 0 | 13 | 0 |
| August | 32°C | 27°C | 36°C | 46% | 57% | 1.6 m/s | 0 | 15 | 0 |
| September | 31°C | 27°C | 35°C | 47% | 58% | 1.7 m/s | 0 | 21 | 0 |
| October | 30°C | 26°C | 35°C | 62% | 58% | 1.4 m/s | 0 | 20 | 0 |
| November | 29°C | 26°C | 34°C | 76% | 60% | 1.6 m/s | 1 | 33 | 0 |
| December | 29°C | 26°C | 33°C | 67% | 58% | 2.2 m/s | 4 | 49 | 0 |
High and low are the warmest and coolest of four readings a day — midnight, 6am, noon and 6pm — so a true overnight low can sit a degree or two under them. Chance of rain, cloud and wind are the day’s average; feels-like and the three ratings (each out of 100: Good from 55, Ideal from 80) are read at midday.
Seasons, and the year in short Ko Samui weather by season
Year round, Ko Samui has days of about 29°C at their warmest in December, its coolest month, and 32°C in May, its warmest; the coolest hours of the day run from 26°C to 28°C through the year, and the average temperature over the year is 29°C around the clock. Rain is most likely around November and least likely around August. Every figure here is a decade of observations blended into one representative year, so it reads as what this date is usually like, not a forecast for one particular day.
Ko Samui weather in winterDecember to February
Winter in Ko Samui has typical daily highs of about 29°C and lows of about 26°C, with a 61% chance of rain on a given day.
Ko Samui weather in springMarch to May
Spring in Ko Samui has typical daily highs of about 31°C and lows of about 28°C, with a 60% chance of rain on a given day.
Ko Samui weather in summerJune to August
Summer in Ko Samui has typical daily highs of about 32°C and lows of about 27°C, with a 52% chance of rain on a given day.
Ko Samui weather in autumnSeptember to November
Autumn in Ko Samui has typical daily highs of about 30°C and lows of about 27°C, with a 62% chance of rain on a given day.
When is the rainy season in Ko Samui?
The rainy (wet) season in Ko Samui runs from October to December, peaking in November with a 76% chance of rain on a given day. The dry season is June to September; August is the driest month, at 46%.
What time of year is Ko Samui windiest?
Winds in Ko Samui are highest in February, averaging 2.9 m/s (10 km/h), and lightest in October, at 1.4 m/s (5 km/h). The prevailing wind is from the SE.
What is the average temperature in Ko Samui year round?
The average temperature in Ko Samui over the whole year is 29°C. May is the hottest month, with highs of about 32°C; December is the coldest, with lows of about 26°C.
Where to go instead in early March, the weakest time here for being outside
How this is worked out
Every figure is a decade of weather-station observations blended into one typical year, in ten-day sections. The ratings, the chart and the feels-like column are read at midday local solar time. Being outside is the Easy outdoors rating, Sun is Sunbathing and Walking is Active outdoors, each out of 100: Good from 55, Ideal from 80. They describe what a time of year is usually like here, not a forecast. The dotted links open the map at that time of year; set its time of day to midday to see these numbers.