September in Muswellbrook is the windiest month of the year. In September, the weather in Muswellbrook is typically warm. Average daily high temperature in September is about 20 degrees above zero. On average, Muswellbrook has 24 sunny, 4 partly cloudy, and 2 rainy days in September. The rains are usually light. September as well as October is considered the most comfortable time to visit Muswellbrook.