Remember that in the Chicago heat waver, there was a stretch of a few days with temps over 100, heat indices in the upper 110s, and lows in the upper 70s, lower 80s. It was the humidity that just made it absolutely brutal. Dew points were in the upper 70s. At Midway (where I live) the heat index hit 125F on July 13, the peak of the heatwave (high 104, low 81 at ORD.)
I remember picking up double shifts left and right that week, as my job was fully air-conditioned, but my room was not.