Warm
Average highs sit around 31°C, giving warm days by monthly-average standards.
September verdict
Koh Samui, Thailand in September
Weather score61Good
Good for holiday weather
Average highs sit around 31°C, giving warm days by monthly-average standards. Sunshine averages 5.5h per day, enough for a balanced month. Rainfall averages 141mm, so some wet days are possible.
September weather
Monthly averages
Temp
31°C
Rain
141mm
Sun
5.5h
Sea
29°C
Weather score
61
Good
Seasonal climate calendar
TemperatureTemp
RainRain
SunSun
SwimSwim
Weather scoreWeather score
Trip feel
Showers
Rainfall averages 141mm, so some wet days are possible.
Some sun
Sunshine averages 5.5h per day, enough for a balanced month.
Warm sea
Sea temperatures average 29°C, so swimming is usually comfortable by monthly-average standards.
Map
Weather map
Compare Koh Samui, Thailand with nearby places by weather score, rain, sun, temperature, and swim conditions.
Temperature
September31°C average high
September is close to Koh Samui's yearly temperature average, giving a typical read on daytime heat.
Warmest monthsApril to September
This stretch sets the upper range for average daytime heat.
Rain
September141mm average rain
September sits on the drier side of Koh Samui's year, which helps with sightseeing and transfers.
Driest monthsJanuary to September
This is the drier part of the year, when outdoor plans usually need less weather flexibility.
Sun
September5.5 hours average sun
September is one of Koh Samui's cloudier months, so sunshine-led plans are less reliable.
Brightest monthsFebruary to April
This stretch has the strongest sunshine in the monthly averages.
Sea temperature
September29°C average sea
September is close to Koh Samui's yearly sea-temperature average, so swimming comfort is fairly typical.
Warmest seaApril to September
Sea temperatures are usually near 30°C in this stretch, so swimming comfort is at its strongest.
Weather score
September61 weather score
September scores below Koh Samui's yearly average, so the weather trade-offs are more noticeable.
Best weather monthsFebruary to March
These months have the strongest weather score in the monthly averages.
