December in Ketchikan is the sunniest and the coldest month of the year. In December, the weather in Ketchikan is typically cold. Average daily high temperature in December is about 2 degrees above zero. On average, Ketchikan has 26 rainy and 5 sunny 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 Ketchikan.