Phuket Island is 48-km long and 21-km across at its widest point, so you're never far from the sea at any given point. The weather is at its best from March to early May and at its wettest from May to October, though mornings and afternoons are still generally sunny and clear. Temperatures tend to be between 25°C on the coolest nights and 33°C on the hottest days.
The basic information below should be studied in advance of a stay on the island to avoid any nasty surprises. There's also plenty of essential information to make your Phuket stay a happy one.