People come in their thousands to Koh Samui each year for their holidays and one of the major reasons is the great weather. Koh Samui weather delivers an average of 6.7 hours of sun each day. All this sun combined with the beautiful warm sea and sand delivers the perfect holiday combination.
The weather in Koh Samui can best be described as typical tropical monsoon climate. Generally humidity is quite high and average temperatures average around 27.5 °C (or 84 °F). This means that you will find that the weather is generally good whatever time of year you visit and rest assured you are very unlikely to feel cold. Due to its location in the gulf of Thailand, Samui's weather is relatively dry in comparison to Phuket and most of Southern Thailand.
Warm seawater temperature is one of the big attractions of a holiday on the island. The sea around Koh Samui stays quite constant throughout the year at a very comfortable 29 °C.
Whilst the weather does get a few degrees hotter in the summer and a few colder in the winter the changes are not that dramatic. However there are three distinct weather seasons on Koh Samui. These are the dry season (December until February), the hot season (March until August) and the rainy season (September until November).
December - February is usually considered as the dry season. In this period the island has slightly cooler temperatures, a small amount of rain and light winds which makes for calm seas. For many visitors this is thought of as the best time to come. Hotels usually have this as the peak season.
March - August is the hotter season on Samui. The weather is still dry in this period, typically very sunny and hot. For visitors who like to bask in the sun this is a great period to visit.
September - November is the the monsoon season. The weather will remain hot and visitors can expect plenty of sunny days. However on some days you will experience monsoon showers. These rain showers are often short but intense lasting for 20 to 60 minutes only.