There seems to be a difference in opinion amongst the travel pundits as to when is the best time of year to visit Koh Lanta. From our experience, we have found that the high season (dry and sunny) starts in Mid-November and continues until the end of May. The temperatures average between 28 C in November up to 36 C May. Even in the low season (green season), it is normal for Koh Lanta to have many days of sunshine. Because Koh Lanta is situated on the west coast of Thailand, it has a frequent cool breeze which makes for a very comfortable climate during the hot months of the year.
Sunscreen and hats are a must! The climate can be particularly deceptive! Remember, those UV rays reflect off the water too, so wear appropriate sun protection at all times!