December in Illinois typically brings the onset of meteorological winter, characterized by cold temperatures, potential snowfall, and decreased daylight hours. Average high temperatures range from the low 30s (F) in the north to the low 40s (F) in the south, while overnight lows often dip into the 20s (F) or lower. Precipitation can occur as rain, snow, or a mixture of both, depending on specific weather systems and location within the state.
Understanding the typical climate conditions during this period is essential for residents, businesses, and visitors. Preparation for winter weather, including potential travel disruptions due to snow or ice, is crucial for safety and minimizing economic impact. Historical weather data for December provides valuable insights for long-term planning in sectors such as agriculture, transportation, and energy. Furthermore, awareness of typical December weather patterns can inform decisions related to outdoor recreation and seasonal events.