December in Nanaimo is the coldest month of the year. In December, the weather in Nanaimo is typically cold. Average daily high temperature in December is about 4 degrees above zero. On average, Nanaimo has 22 rainy, 5 sunny, 2 cloudy, 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 Nanaimo.