The Koh Phangan weather and climate chart below is based on average rainfall and temperature levels for the Surat Thani region of Thailand.
As you can see, there are some quite considerable differences in weather patterns throughout the year.
As Koh Phangan has a tropical climate – and is therefore consistently warm throughout the year – you would be better off planning your visit around expected rainfall levels rather than temperature.
General prevailing Koh Phangan weather conditions
To begin with, avoid September through November if you are looking for a rain-free trip as this is when the southern monsoon rains hit Koh Phangan the hardest. The best months to visit for clear blue skies and calm seas are February to March, with March being one of the hotter months on average (28°C). April (especially the back-end of the month) to May tends to be hot and humid and the conditions can be a little stifling at this time. July to August is a good time to come to Koh Phangan because temperatures are nice and warm and there are only moderate rainfall levels compared with some other months of the year.
How could the weather affect your plans?
Another thing to think about is how the weather will affect any activities you are planning to do whilst on Koh Phangan. If you are coming here to go diving, consult local dive operators to find out when underwater visibility is generally at its best before making any bookings. Also, boat journeys to all of the islands beaches are not possible at all times of the year. For example, the short longtail ride from Ao Chaloklam to Bottle Beach is not possible during times of heavy winds and rainfall as the sea around the headland becomes too choppy.
Remember, Koh Phangan is in a tropical part of the world and as such the climate there can be unpredictable at times. However, if you observe the general weather patterns of the region then you will give yourself the best chance of getting the Koh Phangan weather you wanted during your visit.