Koh Tao weather is similar to most of Thailand; characterised by sub-tropical climate and a monsoon season.
More than 300 days of sunshine can be enjoyed by visitors each year provided that you go at the right time.
Koh Tao Weather, 7 Day Forecast, Island Climate, Sunshine & Rain
The dry season here is from December to February, and while the absence of rain is never a guarantee, these months see the least chances of rain. There may be occasional rainfall, but they tend to clear out rather quickly.
This is also the most popular period to visit the island thanks to lower humidity levels and lots of sunshine, plus amazing tropical temperatures suitable for spending lots of time outdoors and at sea. Additionally, these months also translate to around 7 hours of sunshine each day, and sometimes as much as 8 hours by February.
The hottest time of Koh Tao weather is from March to August. This is when the area experiences the south-west monsoon, and the weather drastically changes. It gets much wetter and hotter compared to the dry season, although there are still sunny, clear days especially during the start of the season. But even during the rainy monsoon season, the island is protected by the surrounding islands and the mainland, so it receives less rain than the nearby islands. March through April is generally dry, but the chances of rainfall increase in May.
If you travel during the hottest months of March to May, be prepared. Always make sure to stay hydrated and protected from the sun. Sunshine levels decrease from May onwards, down to around 6 hours a day.
September to November is the wet season, and torrential rains are expected, as well as flooding and some tropical storms.