About Lightning in Illinois
Illinois averages 40 thunderstorm days per year, placing it above the national average of 25 days. Located at approximately 40°N latitude, Illinois is stretching from the Great Lakes to the confluence of the Mississippi and Ohio rivers, with flat terrain that allows storm systems to sweep across the state unimpeded.
In Illinois, frontal boundaries and warm moist air from the south converge across flat terrain. Peak thunderstorm activity occurs during May through August, when conditions align for the most frequent lightning strikes. With a population of 12.8 million residents, storm awareness and lightning safety are critical concerns for anyone living in or visiting Illinois.