In August, the weather in Koh Lanta Yai is typically hot. Average daily high temperature in August is about 29 degrees above zero. On average, Koh Lanta Yai has 28 rainy, 2 sunny, and 1 cloudy day in August. The rains are usually heavy. August as well as April, May, June, and July is considered the most uncomfortable time to visit Koh Lanta Yai.