Fortunately for beach lovers, Thailand’s two coasts have slightly different rainy seasons, allowing visitors to find sunny beaches nearly year round. On the Andaman or west coast, where Phuket, Krabi, and the Phi Phi Islands lie, the southwest monsoon brings heavy storms from April to October, while on the Gulf of Thailand or east coast, where Koh Samui, Koh Phangan, and Koh Tao lie, the most rain falls between September and December. While the monsoon on the west coast brings a fairly steady season of continual rain that forces businesses outside the major tourist destinations to shut their doors for the season, the east coast storms are more similar to the north’s, generally sunny days with occasionally heavy downpours.
Overall, the southern parts of Thailand, particularly the Andaman Coast, get the most rain: around 2,400 millimeters every year, compared with the central and northern regions of Thailand, both of which get around 1,400 millimeters.