Not that cool.
From
https://weatherspark.com/averages/30851 ... ted-StatesQuote:
Average Weather On June 23 For Chicago, Illinois, USA
Location
This report describes the typical weather at the Chicago Midway International Airport (Chicago, Illinois, United States) weather station over the course of an average June 23. It is based on the historical records from 1974 to 2012. Earlier records are either unavailable or unreliable.
Chicago, Illinois has a humid continental climate with hot summers and no dry season. The area within 25 miles of this station is covered by built-up areas (36%), oceans and seas (24%), grasslands (23%), croplands (14%), and forests (3%).
Temperature
The temperature typically varies from 66°F to 80°F and is rarely below 57°F or above 90°F.