December in Dallas is the cloudiest month of the year. In December, the weather in Dallas is typically warm. Average daily high temperature in December is about 12 degrees above zero. On average, Dallas has 15 partly cloudy, 11 sunny, 4 rainy, and 1 cloudy day in December. The rains are usually light. December as well as January, February, July, and August is considered the most uncomfortable time to visit Dallas.