April in Gillette is the cloudiest month of the year. In April, the weather in Gillette is typically warm. Average daily high temperature in April is about 11 degrees above zero. On average, Gillette has 17 rainy, 6 sunny, 5 partly cloudy, and 2 cloudy days in April. The rains are usually heavy. April as well as March and May is considered the most uncomfortable time to visit Gillette.