The climate in Koh Tao Thailand is generally hot and sunny all year round. Except for monsoon season which begins at the end of October and continues into the beginning of December, travelers should expect to have sunny and humid temperatures on the island. With the islands close geographical proximity to the equator, summer is the main season on Koh Tao.
During December the temperatures are steady between 22*C at night and rising to about 29*C during the day. Given that this is considered the winter in Koh Tao, the island may have some overcast days and a light breeze/ wind should be in the air as a welcomed relief from the heat.
From January onwards, the temperatures begin to climb with April, May and June being the hottest months of the year. There is very little to no rain during this period and the winds have also died down. During this time daily dips in the Ocean to cool down are necessary. Diving offers a great relief from the heat, as well air conditioned accommodation provides a haven from the sweltering sun.
By July, the temperatures cool down a little bit with the changing winds. Koh Tao experiences the return of a breeze and cooler evening temperatures. From July until October there is a slight cooling down as the climate prepares for the return of the monsoon. In the monsoon months, one can expect regular thunderstorms as the island is being nourished with water necessary for vegetation and personal supplies. Roads are likely to flood during this time and most travelers head to the West side of Thailand to enjoy a summer season on the islands in the Andaman Sea. For those sticking around during monsoon, dive shops are still operational, most business are open with a more relaxed schedule and bargains can be found when hunting for guest houses. There is a more relaxed vibe on the island during monsoon, as some business are renovating for the upcoming season, and others take a holiday before the Christmas rush arrives.
It must be noted that the sun in Koh Tao can be very strong and sunburns are extremely common. Even during the overcast days, or whilst doing any water activities, travelers should protect themselves with high spf sunscreen, light long clothes for longer sun exposure and most importantly drink plenty of water. Many complaints at the local traveler health clinics are related to heat stroke, sun stroke, and severe dehydration. With proper care and supplies, any traveler can enjoy the hot island paradise.