The Andaman coast around Satun experiences the opposite monsoon pattern to the Gulf of Thailand — the dry season here runs from November to April, when the sea is calm, visibility is excellent for diving and snorkelling, and the ferry services to the islands run reliably. This is the time to visit if the Tarutao islands are your goal.
From May to October, the southwest monsoon brings heavy rain and strong winds. The Tarutao National Marine Park is officially closed and the island ferries stop. Satun town itself and Thale Ban National Park remain accessible but the weather is wet and the roads can be slippery.
January and February are the most reliably settled months, with calm seas and clear skies. The Ko Lipe diving and snorkelling is at its best from January to April, when visibility can reach 30 metres.