How often does severe weather hit near the Chicago metropolitan area every year?

Dear Tom,
How often does severe weather hit near the Chicago metropolitan area every year?
— Kirk Light, Hanover Park

Dear Kirk,
The Chicago office of the National Weather Service, located in Romeoville, has severe weather warning responsibility for 23 counties in north-central and northeast Illinois and far northwest Indiana.

Lead forecaster Mark Ratzer checked the records and found that, on average, portions of that area are included in a severe thunderstorm watch about 15 days each year and a tornado watch on six days. Ratzer also tallied warning data for the 10-year period from 2008 to 2017 and noted that severe thunderstorm or tornado warnings, for any portion of that area, were issued on an average of 28 days a year — ranging from a maximum of 34 days in 2008 to just 21 days in 2016.

Parts of the Chicago area are included in a severe thunderstorm watch about 15 days each year and a tornado watch on six days.