July in Jamestown is the sunniest and the warmest month of the year. In July, the weather in Jamestown is typically warm. Average daily high temperature in July is about 26 degrees above zero. On average, Jamestown has 20 sunny, 8 partly cloudy, and 3 rainy days in July. The rains are usually light. July as well as August and September is considered the most comfortable time to visit Jamestown.