We are quite lucky here in Gulf of Thailand since our diving season lasts almost through the year and therefore we are open the whole year as well. Usually the weather in Koh Tao is more or less sunny but the biggest possibility for having rainy days is during November when the winds are at the strongest and the waves might get huge. In many years, however, november has also provided us sunny days and the rainy day's rain showers have only lasted an hour or two.
In addition, since Koh Tao is a small island in a middle of the ocean, it´s difficult to predict the weather perfectly. In order to get some sort of knowledge about it, we are using the following website: