In December, the weather in Amherst is typically cold. Average daily high temperature in December is about 2 degrees above zero. On average, Amherst has 10 partly cloudy, 7 sunny, 6 cloudy, 5 rainy, and 3 snowy 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.