January in Hattiesburg is the coldest month of the year. In January, the weather in Hattiesburg is typically warm. Average daily high temperature in January is about 12 degrees above zero. On average, Hattiesburg has 13 sunny, 11 rainy, and 7 partly cloudy days in January. The rains are usually heavy. January as well as July and August is considered the most uncomfortable time to visit Hattiesburg.