September in Arusha is the sunniest month of the year. In September, the weather in Arusha is typically warm. Average daily high temperature in September is about 25 degrees above zero. On average, Arusha has 20 partly cloudy, 8 sunny, and 2 cloudy days in September. September as well as May, June, July, and August is considered the most comfortable time to visit Arusha.