Warm
Average highs sit around 31°C, giving warm days by monthly-average standards.
Weather Guide
Koh Samui, Thailand Average Monthly Weather
Weather score65Good annual avg
Best months: February, March, January
Across the year, average daytime temperatures are around 30°C, sunshine averages 6.5h per day, and rainfall totals about 1941mm. Sea temperatures average 29°C across the year.
Annual weather
Annual averages
Temp
30°C
Rain
1941mm
Annual total
Sun
6.5h
Sea
29°C
Weather score
65
Good avg
Seasonal climate calendar
TemperatureTemp
RainRain
SunSun
SwimSwim
Weather scoreWeather score
Trip feel
Showers
Rainfall averages 146mm, so some wet days are possible.
Some sun
Sunshine averages 5.8h per day, enough for a balanced month.
Warm sea
Sea temperatures average 30°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
July31°C average high
July sits in the warmer part of the year, so midday sightseeing can feel heavier than in cooler months.
Warmest monthsApril to September
This stretch sets the upper range for average daytime heat.
Rain
July146mm average rain
July 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
July5.8 hours average sun
July 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
July30°C average sea
July sits in the warmer sea-temperature season, usually making swimming easier to enjoy.
Warmest seaApril to September
Sea temperatures are usually near 30°C in this stretch, so swimming comfort is at its strongest.
Weather score
July61 weather score
July 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.
