December in Markham is the windiest month of the year. In December, the weather in Markham is typically freezing. Average daily high temperature in December is about zero. On average, Markham has 12 cloudy, 11 snowy, 6 rainy, and 2 sunny days in December. The snowfalls are usually moderate. December as well as March, April, October, and November is considered the most uncomfortable time to visit Markham.