September in Warrnambool is the windiest month of the year. In September, the weather in Warrnambool is typically warm. Average daily high temperature in September is about 15 degrees above zero. On average, Warrnambool has 23 rainy, 4 sunny, 2 cloudy, and 1 partly cloudy day in September. The rains are usually moderate. September as well as May, June, July, and August is considered the most uncomfortable time to visit Warrnambool.