In September, the weather in Saint Johnsbury is typically warm. Average daily high temperature in September is about 18 degrees above zero. On average, Saint Johnsbury 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 Saint Johnsbury.