January in Dumas is the coldest month of the year. In January, the weather in Dumas is typically cold. Average daily high temperature in January is about 9 degrees above zero. On average, Dumas has 14 sunny, 10 rainy, 6 partly cloudy, and 1 cloudy day in January. The rains are usually heavy. January as well as February and August is considered the most uncomfortable time to visit Dumas.