December in Mahwah is the cloudiest month of the year. In December, the weather in Mahwah is typically cold. Average daily high temperature in December is about 4 degrees above zero. On average, Mahwah has 11 cloudy, 10 rainy, 5 sunny, and 5 partly cloudy days in December. The rains are usually heavy. December as well as January, February, and March is considered the most uncomfortable time to visit Mahwah.