January in Naperville is the snowiest, the cloudiest, and the most freezing month of the year. In January, the weather in Naperville is typically freezing. Average daily high temperature in January is about 3 degrees below zero. On average, Naperville has 15 cloudy, 10 snowy, 4 sunny, 1 rainy, and 1 partly cloudy day in January. The snowfalls are usually moderate.