What is Chicago’s record heat index?

Dear Tom,
What is Chicago’s record heat index? My guess is around 120.
— Gary Janssen, Elk Grove Village
Dear Gary,
You are close, but it is even higher. Chicago’s highest heat index, while not official because it was recorded at Midway Airport, stands at 125 degrees. It was recorded during the city’s deadly 1995 heat wave that was responsible for 739 fatalities. On July 13, 1995, Midway Airport logged a sweltering high temperature of 106 degrees, that, in conjunction with an Amazon-jungle level 81-degree dew point, produced the 125-degree heat index record. As suffocating and oppressive as conditions were in Chicago that day, the heat and humidity can be much worse. The world’s highest recorded heat index stands at 178, set at Dhahran, Saudi Arabia, on July 8, 2003, with a temperature of 108 and a dew point of 95.
Chicago typically has hot and humid summers, but the record-highest heat index was recorded at Midway during 1995. That year, 739 people died during the heat wave.