Phuket has a tropical monsoon climate. Its warm all year around, but the two periods of April-May and September-October are the hottest.
The best time to visit Phuket is during the cool NE monsoon season, from November though March, when it isn't so humid, and the cool breezes keep things comfortable. The average temperature is around 75°F to 89°F (24°C to 32°C).
The hottest time is from April through May, with temperatures ranging from 80°F to 95°F (27°C to 36°C). There are frequent short heavy thundery showers, offering welcome relief from the temperature and humidity. The Thai New Year occurs on April 13th and everyone sprinkles (or throws) cool water on each other.
The locals enjoy June, July and August, since the weather is usually fine and favourite haunts remain uncrowded. The usual pattern is brief but heavy showers, with plenty of sunshine between downpours. Everything is a little less expensive at this time of year, as well. Temperatures range between 70°F and 90°F (20°C to 33°C).
During September and early October sailors begin to batten the hatches. This makes an ideal time to haul out and visit abroad. One consolation for those who remain is that the the anchorages, outdoor restaurants and cruising grounds are relatively uncluttered by visitors. And even at this time, there are still long intervals of sunshine between the heavy showers