The weather in Samui in May is as hot as it gets, with temperatures at an average of 30°C/85°F and hitting daily highs over 34°C/93°F. At the same time, an increase in rainfall – up to about 160mm dropping over nine days – leads to higher humidity, with daily averages between 62% and 92%. So long as you’re happy with the heat, though, the weather is generally good, with plenty of sunshine. Conditions on the water slowly start to deteriorate towards the end of the month, with the wind now coming from the west and waves picking up enough that diving and snorkelling become less practical on the west coast (but definitely still possible on the east coast). The sailing season now starts, and it comes in with bang as the Samui Regatta dominates the final week of the month. Water temperatures remain at their hot season high of 28°C/82°F.