In July, the weather in Koh Lanta Yai is typically hot. Average daily high temperature in July is about 28 degrees above zero. On average, Koh Lanta Yai has 24 rainy, 6 cloudy, and 1 sunny day in July. The rains are usually heavy. July as well as April, May, June, and August is considered the most uncomfortable time to visit Koh Lanta Yai.