Climate Overview
The climate in Ko Samui is cold. The average annual temperature is 2°C and approximately 342mm of precipitation falls per year. October is the wettest month, receiving around 33mm of rainfall. Ko Samui sits near the equator, so seasonal temperature differences are minimal throughout the year. Snowfall occurs from January to December, with around 163cm accumulating over the season.
Temperature
Ko Samui has relatively stable temperatures year-round, staying within a 6°C range. January is the warmest month, though highs remain moderate at 5°C with a mean of 3°C. The coldest month is December, when overnight lows fall to -1°C and the daily average is -1°C. Daily temperature variation is modest, with an average difference of 2°C between highs and lows.
Precipitation
Ko Samui is a quite dry location, receiving approximately 342mm of precipitation annually, which averages out to around 29mm per month. The wettest month is March, averaging 33mm of rainfall. April and May also tend to see above-average precipitation. The driest month is December, with just 9mm. That's 24mm less than March, the wettest month. Precipitation varies noticeably between seasons, with the first half (January to June) of the year generally seeing more rainfall. Snowfall is a regular feature from January to December, with around 163cm accumulating over the season. May typically sees the most snow at around 33cm.
Wind
Ko Samui is mildly breezy, with an average annual wind speed of 13km/h. For context, sustained winds below 12km/h are generally light, while anything above 25km/h is considered strong. The windiest month is May, averaging 16km/h, though still comfortable for most outdoor activities. The calmest conditions occur in January, with average winds dropping to 7km/h, making it an ideal period for wind-sensitive activities. Wind speeds vary significantly across the year, with a 9km/h difference between the calmest and windiest months. This level of variation is worth factoring into travel plans. Wind tends to pick up during the summer months. The seasonal averages are 9km/h in winter, 15km/h in spring, 12km/h in summer, 15km/h in autumn.
Seasons
16 days until Autumn
It is currently summer in Ko Samui, which began on June 21, 2026. Ko Samui sits near the equator, so the traditional four-season cycle is less pronounced. Temperatures remain relatively stable year-round. The warmest period peaks in January at around 5°C, while the coldest stretch bottoms out in December near -1°C. Autumn is next, beginning on September 23, 2026 (16 days from now).
Spring
Temperatures range from 0 to 3°C. Rainfall is relatively light, with around 98mm over the season and a monthly average of 33mm. Winds are generally light, averaging 15km/h. Light layers work well as temperatures warm through the season. It is a great time to be outdoors.
Summer
Temperatures range from 0 to 3°C. Rainfall is relatively light, with around 98mm over the season and a monthly average of 33mm. Winds are generally light, averaging 12km/h. Comfortable clothing with a light layer for cooler evenings is all you need.
Autumn
Temperatures range from -1 to 3°C. Rainfall is relatively light, with around 82mm over the season and a monthly average of 27mm. Expect around 8cm of snow accumulation during this period. Winds are generally light, averaging 15km/h. Layered clothing works best as temperatures gradually cool. Enjoy the crisp air and changing scenery.
Winter
Temperatures range from -1 to 5°C. Rainfall is relatively light, with around 64mm over the season and a monthly average of 21mm. Expect around 16cm of snow accumulation during this period. Winds are generally light, averaging 9km/h. Warm winter clothing and waterproof boots are a must, and travel may be affected by snow.
Monthly Climate Data
The table below shows monthly climate averages for Ko Samui based on historical weather data. Min and max temperatures represent typical overnight lows and afternoon highs for each month, shown in degrees Celsius (°C). Precipitation is measured in millimetres (mm) and indicates the average total rainfall per month. Snow is measured in centimetres (cm) and reflects average monthly snowfall accumulation. Wind speed is the average sustained speed in kilometres per hour (km/h). All values are based on averages from over 10 years of historical weather data. The current month is highlighted for quick reference.
