December in New Westminster is the coldest month of the year. In December, the weather in New Westminster is typically cold. Average daily high temperature in December is about 4 degrees above zero. On average, New Westminster has 20 rainy, 6 sunny, 4 partly cloudy, and 1 cloudy day in December. The rains are usually heavy. December as well as January, February, March, and April is considered the most uncomfortable time to visit New Westminster.