Ko Samui has two seasons, sunny and rainy. The best time to visit the island is without a doubt late December through September. Coming in the off months means heavy rains and potentially torrential storms.

Ko Samui weather can become incredibly hot; those affected by weather should consider what month is best for them. December to February & August September are traditionally the best time to go if you are easily affected by the heat where the weather averages around 30c. March through June remains high-season with temperatures climbing to around 35-36c . Plenty of sunshine and very little rain exists during this period. October and November are the rainiest months, however, compared to main land Thailand, Ko Samui does not suffer nearly as much rain during what's considered the "rainy season".Best times beach & water wise for Samui are March to September

There are several fabulous festivals that will greatly highlight any visit to Ko Samui. One of the biggest events is the Thai New Year or " Songkran" on April 13. The word comes from Sanskrit meaning "new year" and the holiday itself was probably brought in from India as much as 2,500 years ago to Thailand and brought into Ko Samui later in its existence with the country. On Songkran day, people everywhere douse each other with water, if this doesn't sound fun to you, the parades and feasts taking place should make up for it.

The Ko Samui Music Festival is a grand celebration and one of Asia's largest music fests. Although, tourists should carefully consider coming in for the festival as it takes place September through October.