September in Ko Samet is the rainiest and the coldest month of the year. In September, the weather in Ko Samet is typically hot. Average daily high temperature in September is about 30 degrees above zero. On average, Ko Samet has 28 rainy, 1 cloudy, and 1 partly cloudy day in September. The rains are usually heavy. September as well as March, April, May, and June is considered the most uncomfortable time to visit Ko Samet.