August in Hamilton is the rainiest month of the year. In August, the weather in Hamilton is typically warm. Average daily high temperature in August is about 13 degrees above zero. On average, Hamilton has 19 rainy, 10 sunny, 1 cloudy, 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 Hamilton.