September in Greeley is the sunniest month of the year. In September, the weather in Greeley is typically warm. Average daily high temperature in September is about 25 degrees above zero. On average, Greeley has 24 sunny, 5 partly cloudy, and 1 rainy day in September. September as well as {{month_nom: February}}, and {{month_nom: February}} is considered the most comfortable time to visit Greeley.