March in Hermiston is the rainiest month of the year. In March, the weather in Hermiston is typically warm. Average daily high temperature in March is about 12 degrees above zero. On average, Hermiston has 10 rainy, 9 partly cloudy, 6 sunny, and 6 cloudy days in March. The rains are usually light. March as well as January and December is considered the most uncomfortable time to visit Hermiston.