December in Chattanooga is the cloudiest month of the year. In December, the weather in Chattanooga is typically cold. Average daily high temperature in December is about 9 degrees above zero. On average, Chattanooga has 12 rainy, 8 sunny, 7 partly cloudy, and 4 cloudy days in December. The rains are usually heavy. December as well as January and February is considered the most uncomfortable time to visit Chattanooga.