July in Bismarck is the sunniest and the warmest month of the year. In July, the weather in Bismarck is typically warm. Average daily high temperature in July is about 27 degrees above zero. On average, Bismarck has 20 sunny, 8 partly cloudy, and 3 rainy days in July. The rains are usually heavy. July as well as August and September is considered the most comfortable time to visit Bismarck.