ILLINOIS — Measurable snowfall is a common and well-documented occurrence in Illinois during the month of January, based on long-term climate records and historical weather data.
According to data compiled by the National Weather Service, January is typically the snowiest month of the year for much of Illinois. Average snowfall totals vary by region, but most areas of the state record measurable snow during the month.
Northern Illinois, including the Chicago area, generally sees higher January snowfall averages, often ranging from 10 to 15 inches. Central Illinois typically records lower but still notable amounts, commonly between 5 and 8 inches, while southern Illinois usually averages a few inches of snow during January.
Snowfall in January is largely driven by frequent cold air intrusions from Canada combined with storm systems moving through the Midwest.
These systems can produce widespread snow, lake-effect snow near Lake Michigan, or lighter snow events depending on atmospheric conditions. Temperatures during January are often cold enough across the state to support snow rather than rain, particularly during overnight and early morning hours.
Historical records show that measurable snowfall — defined as at least one-tenth of an inch — occurs multiple times during a typical January in Illinois. Even in milder winters, most locations still record at least one measurable snowfall during the month. Conversely, some years have produced significantly above-average snowfall, including multi-day snow events and major winter storms.
While snowfall amounts can vary widely from year to year and location to location, long-term climate data clearly indicates that measurable snowfall in Illinois during January is a regular and expected part of the state’s winter climate.
