It is warm in Phuket all year round with temperatures ranging between 25 – 34°C (77 – 93°F). Phuket’s weather is typically divided into two distinct seasons, dry and rainy, with transitional periods in between. The seasons are dictated by the tropical monsoon, which is characterized by prevailing winds that blow from the northeast for half the year, then reverse and blow from the southwest, producing a dry season and a wet season.
The dry season begins in December and usually lasts until March. The northeast monsoon draws cool, dry air from the Asian continent resulting in a slight drop in temperature. This is the high season for tourism in Phuket, when the climate is at its best, characterized by gentle breezes, calm seas and clear blue skies. It is also the coolest time of year.
The transitional periods last a month or so. During these periods the weather is often hard to predict. The period before the rainy season, around April – May, is the hottest time of year. There may be a lot of rain or none at all. The October – November transition is cooler and usually quite wet.
The rainy season begins in June and lasts until October. When people talk about the monsoon season, they are referring to the southwest monsoon period, which is the rainy season. The strong winds bring warm moist air from the Indian Ocean and plenty of rain. This is Phuket’s low season. The average rainfall in Phuket is about 2500mm or about 100 inches, with the vast majority of it falling within this period. Its hot, humid and wet!
Another aspect of the southwest monsoon is that the seas around the island can be quite rough. Two-metre seas are typical, with many rain squalls. This affects boat tours and ferries, often prohibiting boat trips to other islands. Stirred silt reduces visibility for divers, and although visibility can sometimes be good, stormy seas often prevent diving at exposed sites. For liveaboards, there are dive companies that operate excursions during the rainy season, however, these are not very regular and dependent on the weather.
On the plus side, the lower volume of tourists during this period means that prices are considerably lower.
As the weather during the rainy season is by no means unpleasant, this can be ideal for the traveller on a budget or who simply wishes to avoid the crowds during the high season. There can be periods of several days that are dry, and when it does rain it is very unusual for it to rain all day.
Extra care should be taken when swimming in the sea from May – October due to strong currents and rough surf.