The weather in Phuket and the whole of Thailand is dictated by the monsoon winds. Yes, winds. An often misconception is that monsoon means rain.
It is true that the South-West monsoon brings “wetter weather” with sometimes heavy thunderstorms and downpours. This wind prevails the months of June until September, sometimes starting already in May and lasting until October.
Monsoon does not mean that it rains all the time. It might be just some 20 minutes downpours a day, with periods of many days without even a drizzle. Usually the best months are July and August.
I call it “green season” and for me it is the best time to visit Phuket. It is less crowded and everything slows down a bit. The beaches are empty, traffic is light, easier to find a good table in a restaurants and the staff is more relaxed as well. And of course when visiting: prices for accommodation and flights are lower; you can get really good deals.
Drawback is that swimming from the beach can be very dangerous, due to big waves and dangerous surf.
If you intend to visit Phuket for water sports like swimming and snorkeling, the solution is easy: Charter your own yacht with Phuket Boatcharter.
Speaking about big waves, this might sound funny, but the explanation is simple. The boat always anchors in a wind protected bay, so there is no need to enter the water trough the dangerous surf at the beach.
Getting to those bays is easy enough. The advantage of the cruising grounds of Phuket are the many hilly islands, providing shelter from the wind. Those islands can be reached in two/three hours sailing. On the way it might get a bit bumpy, but since we only do coastal sailing, all is very safe.
And the same advantage of less crowded applies for sailing trips as well. When staying overnight, sometimes you have the anchorage / bay just for you and your private yacht. All boats come with comfortable cabins and are fully crewed with captain and cook.
From mid October onwards the monsoon changes to North East, bringing dryer and more stable weather, with the hottest month in March and April.
To summarize: Phuket with its always warm climate is an all year destination and always worth a visit. If you want to avoid the crowds visit in “green season” for a fantastic holiday.