Our island is located just 697 miles north of the equator and 1672 miles south of the Tropic of Cancer. So it’s no surprise that the weather on Koh Tao is usually hot! The temperature only varies by around 10-12°C throughout the year, ranging from the mid-20s to mid-30s in Degrees Celsius. High humidity levels can often make it feel much hotter than it is, but our position so close to the equator means that the sun sets somewhere between 6 pm and 7 pm daily. So the temperature does drop in the evening to a much more comfortable level.
Nothing is ever guaranteed, and the continual effects of climate change mean our seasons are becoming less predictable. But in general, the weather on Koh Tao can be described as hot and dry, hot and windy, or wet.
February to May is peak heat season, with the hottest months being March and April. Rainfall is rare, temperatures soar to around 35°C, and there is very little wind or breeze. So if you like it hot, then this is the time to visit – just don’t forget your sunscreen!
From June to October you can expect to experience a few windy days and some cool breezes coming off the ocean. The East coast of Thailand gets most of its monsoon rain between June and August, so sometimes we get some rain during this time too.
Monsoon season on Koh Tao typically starts in November or December and runs through into January. Although we still get some hot, sunny days in between, it’s during these months where we can expect the most rainfall – and often some pretty impressive lightning storms!
For the divers among you planning what to pack, the water temperature varies by about 8°C throughout the year, usually sitting between 26-34°C. So most people find that a short 3mm wetsuit or shorts and a rash vest work just fine for scuba diving throughout the year.
There is no guaranteed ‘season’ for whale sharks on Koh Tao. It just comes down to being in the right place at the right time. That said, the best months for sightings are normally April, May, September, and October, as whale sharks use the changing seasons as a navigational tool for moving into foraging areas.
If you are prone to seasickness, you want to avoid stormy or windy conditions for your dive trips. Although we get great weather on Koh Tao for most of the year, regardless of the season, the flattest seas tend to be in February, March, and September.
Not surprisingly, when the sea is calm, good visibility is usually a given. In February and March, and again from August through to October, visibility can sometimes reach 30 meters plus. You can still dive if you visit in monsoon season, but then visibility may only reach up to 10 meters. For the rest of the year, you can expect average visibility of 15-20 meters on most trips.
Tourists should note that the microclimates in Thailand are incredibly regionalized. So if you are visiting other destinations in Thailand during your stay, be aware that the weather on Koh Tao is likely to be different from what you will find in Phuket, Bangkok, or Chiang Mai at any given time. So do take the time to plan your stay around all locations on your itinerary.