December in Seaside is the coldest month of the year. In December, the weather in Seaside is typically cold. Average daily high temperature in December is about 8 degrees above zero. On average, Seaside has 24 rainy, 5 sunny, and 2 partly cloudy 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 Seaside.