June in Haikou is the cloudiest and the hottest month of the year. In June, the weather in Haikou is typically hot. Average daily high temperature in June is about 32 degrees above zero. On average, Haikou has 28 rainy and 2 sunny days in June. The rains are usually heavy. June as well as May, July, August, and September is considered the most uncomfortable time to visit Haikou.