August in Siheung is the warmest month of the year. In August, the weather in Siheung is typically warm. Average daily high temperature in August is about 27 degrees above zero. On average, Siheung has 19 rainy, 9 sunny, 2 partly cloudy, and 1 cloudy day in August. The rains are usually heavy. August as well as February, July, and December is considered the most uncomfortable time to visit Siheung.