Planning for the weather is an important factor for making your trip to Koh Tao a success, especially when you’re splurging. The hottest months are usually May and June, with an average temperature of 29°C, while the coldest months are January and February, with an average of 27°C. The rainiest months in Koh Tao are November, October, September and December, with each month seeing an average of 274 mm of rainfall.