In December, the weather in Commack is typically cold. Average daily high temperature in December is about 6 degrees above zero. On average, Commack has 11 sunny, 8 rainy, 7 partly cloudy, 4 cloudy, and 1 snowy 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 Commack.