In September, the weather in Amherst is typically warm. Average daily high temperature in September is about 21 degrees above zero. On average, Amherst has 13 sunny, 9 partly cloudy, 6 rainy, and 2 cloudy days in September. The rains are usually light. September as well as {{month_nom: February}}, and {{month_nom: February}} is considered the most comfortable time to visit Amherst.