January in Simpsonville is the coldest month of the year. In January, the weather in Simpsonville is typically cold. Average daily high temperature in January is about 9 degrees above zero. On average, Simpsonville has 15 sunny, 9 partly cloudy, 6 rainy, and 1 cloudy day in January. The rains are usually heavy. January as well as February, March, and December is considered the most uncomfortable time to visit Simpsonville.