September in Derry is the sunniest month of the year. In September, the weather in Derry is typically warm. Average daily high temperature in September is about 21 degrees above zero. On average, Derry has 14 sunny, 10 partly cloudy, and 6 rainy days in September. The rains are usually moderate. September as well as {{month_nom: February}}, and {{month_nom: February}} is considered the most comfortable time to visit Derry.