The sailing season in Koh Samui starts in June when we relocate from Koh Chang to participate in the Koh Samui Regatta, a major Asian sailing event. By this time the southwest monsoon winds have settled in to deliver exhilarating sailing conditions to the western side of the Gulf of Thailand. The yacht charter season ends in September, for soon the wet season will be in full swing.
While all other sailing destinations in Thailand are being battered by the southwest monsoon and remain untenable, Koh Samui is uniquely positioned to benefit. The mountainous terrain of the Malay peninsular to the south west of this island group exhausts the monsoon winds of their rains and leaves Koh Samui and its surrounding islands are basking in sunshine with flat seas and a cool steady breeze.
Weather conditions remain nicely tropical with temperatures ranging from 30C in the daytime to 24C during the night. Wind can range from 10 to 25 knots and although conditions remain mainly dry, there is the chance of scattered squalls.
All in all this is a great place to charter a yacht, with mildly challenging sailing conditions by day and beautiful tranquil anchorages by night.
The Synoptic chart below and the Buoy Weather forecast tool to the left should give you a good indication of what the weather is like now.