August in Sanya is the rainiest month of the year. In August, the weather in Sanya is typically hot. Average daily high temperature in August is about 29 degrees above zero. On average, Sanya has 27 rainy, 3 sunny, and 1 partly cloudy day in August. The rains are usually heavy. August as well as May, June, July, and September is considered the most uncomfortable time to visit Sanya.