December to February is the best time to visit Koh Tao as the weather is warm and sunny and it's the busiest time for the bars and clubs. July to September is the best time to visit for great visibility during diving. March to May is comparatively hot, and visibility isn't great, but whale sharks are common in this period. The months of October and November are the worst time to visit Koh Samui as the rains start hitting the island.
|Month||Avg. Minimum (°C)||Avg. Maximum (°C)|