Aurora received the greatest 24-hour rainfall (16.94 inches) in Illinois history, exceeding the previous record of 16.54 inches at East St. Louis on June 14, 1957. A broad band of 8-inch-plus rainfall from just south of Rockford to a little north of Kankakee exceeded the 7.58 inch threshold regarded as the average 100-year (once every 100 years) 24-hour storm for a given point in northeast Illinois. The deluge in Aurora was considered a 1-in-1,000-year event. The Joliet Brandon Dam measured 13.60 inches, and a gauge in the extreme southwest corner of the Chicago metro area recorded 10.99 inches. Strong thunderstorms hit on the afternoon of the 17th, but the greatest rainfall in most areas occurred in early morning thunderstorms on the 18th.
Wow. Never knew that was a thing. Shared assuming there's at least one other ignoramus like me in here