January in Pontoise is the coldest month of the year. In January, the weather in Pontoise is typically cold. Average daily high temperature in January is about 5 degrees above zero. On average, Pontoise has 13 rainy, 9 cloudy, 5 partly cloudy, and 4 sunny days in January. The rains are usually light. January as well as February, March, May, and November is considered the most uncomfortable time to visit Pontoise.