Koh Samui Weather
The hottest time of year is April, when the locals will good timingly have a three day water fight to celebrate the Thai New Year. Hit the beach but seriously stay covered. The holiday becomes less fun if spent peeling layers of burnt skin off your face.
Thailand's climate is tropical. High in both temperature and humidity. Most people find it pleasant. The average temperature is about 30 degrees Celsius, or 86 degrees Fahrenheit. When it is getting too hot, just enter a air conditioned room or shop for a while and you will "refill your batteries". Remember to drink a lot of water. Even if it is more or less "summer" here year round, you could say that Thailand and Koh Samui has three seasons.
It cools down in December – the rainy season – which brings with it shock floods from the sky that no umbrella, and very few roves, can protect against. Chance of departure from the airport goes down to 80%
The highs are in the 40s and the lows are in the 20s.
There are breezes from the north east – sometimes.
The climate seasons are not exactly the same as in Krabi and Phuket, as these destinations are located in/at the Andaman Sea and Koh Samui, Koh Phangan and Koh Tao are located in the Gulf of Thailand. This makes the climate differences evident.
Best Time to Visit Koh Samui
The best time to visit the Samui group of islands is during the hot, dry season from February to late June. From July to October, during the southwest monsoon, it can rain intermittently, and from October to January, during the northeast monsoon, there are sometimes strong winds. However, many travellers have reported sunny samui weather (and fewer crowds) in September and October. November tends to get some of the rain that also affects the east coast of Malaysia at this time.