December in Grants Pass is the coldest month of the year. In December, the weather in Grants Pass is typically cold. Average daily high temperature in December is about 7 degrees above zero. On average, Grants Pass has 17 rainy, 6 partly cloudy, 5 sunny, and 3 cloudy days in December. The rains are usually heavy. December as well as January, February, March, and April is considered the most uncomfortable time to visit Grants Pass.