Weather in Koh Samui in June

How June compares

June is the 3rd warmest month of the year in Koh Samui and ranks 22nd of 134 destinations we compare for June - see where else is hot in June. Within Thailand it is 3rd of 6 (Thailand in June). Against London's average high of 19.6°C in June, Koh Samui is 10.3°C warmer by day and 15.8°C warmer at night.

Daytime and night-time in June

The typical June day in Koh Samui peaks at 29.9°C, but that is an average: the warmest 10% of days reach 30.9°C or more. About 100% of days top 25°C and 1 in 2 pass 30°C. Nights average 27.1°C; one night in ten drops to 26.2°C or lower, so pack a layer for evenings. Between 1991 and 2020 the hottest June day here reached 32.4°C (2019-06-30) and the coldest night 24.3°C (2019-06-07).

Rain in June

Wet (more than 8 rainy days): about 19 days with 1 mm or more, 93 mm in total. Year to year it varies a lot - the wettest June was 2019 with 145 mm, the driest 2012 with 28 mm. Humidity averages 78%, which makes the heat feel heavier than the thermometer suggests.

Sea temperature in June

The sea averages 30.0°C - warm enough to swim (22°c+). Depending on the year it ranges from 29.4°C to 30.5°C. For the warmest sea here, come in May (30.5°C).

Sunshine and daylight

Around 1.8 hours of sunshine a day (estimated from cloud cover), 12.6 hours of daylight: the sun rises about 06:00 and sets about 18:41 local time in mid-June. Average cloud cover is 86%.

Is June 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.

Expect humid heat with little overnight relief

The heat is consistent enough that you should pack for hot weather throughout your stay, rather than expect cooler days to provide a break. Humidity averages 78%, making shade and breaks from the heat particularly welcome around midday. Loose, breathable clothing is a better choice than heavy fabrics, and prioritising accommodation with air conditioning makes sense when nights remain so warm. The sea averages 30°C, which suits travellers who dislike a chilly swim, although it will offer less cooling than you might hope for. June works best if you enjoy warmth even after sunset; it is less comfortable if you rely on cool evenings to recover.

Keep plans flexible rather than counting on clear skies

Rain is frequent enough to influence how you plan your days, so leave outdoor time flexible and carry a light waterproof. About 1.8 hours of sunshine within 12.6 hours of daylight means you should not confuse long days with long spells of sun. Equally, a rainy day does not necessarily mean rain throughout the day; the monthly figures cannot tell you when dry gaps will arrive. This is a better fit for travellers happy to swim and relax under cloud than for those whose priority is clear skies. Keep sun protection handy even when it looks overcast, and avoid making every day's enjoyment depend on dry weather.