One in four years has drier weather, while another one in four is wetter. Although snow is possible now, in most years December is free of snow. December is one of the cloudiest months for Dallas. The sun's rays reach the ground during 52 percent of daylight hours on average, for a total of 162 hours in the month. Typically on 11 days this month the sky is mainly clear, with at most 30 percent cloud cover.