January in Jacksonville is the coldest month of the year. In January, the weather in Jacksonville is typically warm. Average daily high temperature in January is about 10 degrees above zero. On average, Jacksonville has 14 sunny, 9 rainy, 4 cloudy, and 4 partly cloudy days in January. The rains are usually heavy. January as well as February, March, June, and July is considered the most uncomfortable time to visit Jacksonville.