August in Chilaw is the rainiest and the coldest month of the year. In August, the weather in Chilaw is typically hot. Average daily high temperature in August is about 28 degrees above zero. On average, Chilaw has 29 rainy, 1 sunny, and 1 partly cloudy day in August. The rains are usually heavy. August as well as March, April, May, and June is considered the most uncomfortable time to visit Chilaw.