About Seneca, IL

Seneca is a city of approximately 2,300 people in Illinois, United States. Located in the Central Time Zone at 41.3°N latitude.

Across a typical year Seneca sees about 34 inches of precipitation, with May the wettest month and January the driest. Temperatures range from January lows near 15°F up to July highs around 84°F, averaging 49°F annually — characteristic of a humid continental climate.