The climate and weather on Koh Tao is tropical offering warm weather and a steady water temperature of around 28 degrees Celsius all year. Located just a few kilometers from Koh Samui and Koh Phangan in the gulf of Thailand, weather patterns here are exactly the same as the two bigger sister islands.
Many visitors to come to the island for scuba diving and underwater visibility is a obviously a major factor. March to August sees the hottest time of the year with maximum temperatures averaging between 30 and 35 degrees Celsius. Minimum temperatures average 25 degrees later in the evenings. Few showers are experienced during this time and underwater visibility is good.
The dry season starts in December and remain until February with average max temperatures reaching 32 degrees Celsius. The average minimum is around 24 degrees Celsius. This is a great time for scuba diving with excellent visibility and popular hotels in Koh Tao as well as dive resorts fill up to the brim. It is therefore imperative you book early to avoid disappointment.
The rainy season, bringing poor underwater visibility, starts September and persist until November. During this time the average maximum temperature is around 31 degrees Celsius and the average minimum around 24 degrees Celsius. This period has an average rainfall of 250 mm per month with the highest rainfall, up to 300 mm, experienced in November.
Peak season is from February to April and again July to September. The best diving time is from mid January to end May. June to mid September the area is affected by the monsoon, but is still reasonably good for diving.