In December, the weather in Amherst is typically cold. Average daily high temperature in December is about 3 degrees above zero. On average, Amherst has 11 cloudy, 7 partly cloudy, 6 rainy, 5 snowy, and 2 sunny days in December. The rains are usually heavy. December as well as January, February, March, and April is considered the most uncomfortable time to visit Amherst.