January in Hermiston is the snowiest month of the year. In January, the weather in Hermiston is typically cold. Average daily high temperature in January is about 6 degrees above zero. On average, Hermiston has 13 partly cloudy, 8 cloudy, 6 rainy, 3 sunny, and 1 snowy day in January. The rains are usually light. January as well as November and December is considered the most uncomfortable time to visit Hermiston.