Weather in Koh Samui in October

How October compares

October is the 9th warmest month of the year in Koh Samui and ranks 32nd of 134 destinations we compare for October - see where else is hot in October. Within Thailand it is 5th of 6 (Thailand in October). Against London's average high of 14.6°C in October, Koh Samui is 13.5°C warmer by day and 17.2°C warmer at night.

Daytime and night-time in October

The typical October day in Koh Samui peaks at 28.1°C, but that is an average: the warmest 10% of days reach 29.1°C or more. About 100% of days top 25°C and 1 in 500 pass 30°C. Nights average 25.6°C; one night in ten drops to 24.4°C or lower, so pack a layer for evenings. Between 1991 and 2020 the hottest October day here reached 30.2°C (2018-10-01) and the coldest night 23.3°C (2018-10-22).

Rain in October

Wet (more than 8 rainy days): about 26 days with 1 mm or more, 283 mm in total. Year to year it varies a lot - the wettest October was 2003 with 694 mm, the driest 2002 with 133 mm. Humidity averages 83%, which makes the heat feel heavier than the thermometer suggests.

Sea temperature in October

The sea averages 29.1°C - warm enough to swim (22°c+). Depending on the year it ranges from 28.7°C to 29.7°C. For the warmest sea here, come in May (30.5°C).

Sunshine and daylight

Around 2.0 hours of sunshine a day (estimated from cloud cover), 11.8 hours of daylight: the sun rises about 06:08 and sets about 18:04 local time in mid-October. Average cloud cover is 83%.

Is October a good time to visit Koh Samui?

It is a reasonable choice: hot days but expect showers. The best months for Koh Samui on our scoring are February, March, January; months averaging 25°C or more: Jan, Feb, Mar, Apr, May, Jun, Jul, Aug, Sep, Oct, Nov, Dec.

Hot days, warm nights and a sea suited to swimming

The heat is consistent rather than extreme, with average daytime highs of 28.1°C and night-time lows of 25.6°C. Humidity of 83% means it can feel sticky, so loose, breathable clothing is more useful than heavy layers. Keep anything energetic flexible and take breaks when the midday warmth feels tiring. Evenings offer little cooling, making a comfortably cooled room a sensible priority if you struggle to sleep in heat. The sea averages 29.1°C, comfortably warm for swimming, although that temperature says nothing about conditions on a particular day. Follow local safety advice before entering the water, and treat a swim as a warm soak rather than a way to cool down sharply.

Rain is the deciding factor

October is a wet choice, with about 26 rainy days and only around 2 hours of sunshine a day. There is much more daylight than sunshine, so do not picture long stretches of clear sky simply because it is hot. Keep outdoor plans easy to rearrange, carry a light waterproof and protect anything that needs to stay dry. This month is better suited to someone content to rest during wet weather than someone whose holiday depends on daily sunbathing. The long-haul journey from London also makes that trade-off worth considering carefully. If reliable beach weather is your priority, the warmth alone is not a strong reason to choose October.