In July 1995 a heat wave killed hundreds in Chicago, most of them older residents alone in apartments that never cooled off after dark.
On this day in 1995, Chicago was in the worst stretch of a heat wave that ran from July 12 through July 16. Daily highs reached 93 to 104 degrees, and on the 13th the heat index peaked at 119, a record for the city. Deaths reported to the Cook County Medical Examiner climbed from 49 on the 14th to 162 on the 15th. Studies afterward put the excess death toll for the month at roughly 700.
The pattern in those deaths is what makes the event a case study rather than a weather record. Most of the dead were elderly. Most lived alone, on upper floors of brick buildings that held the day's heat well past midnight. Many had no air conditioning, and some had a unit they could not afford to run. A number kept windows closed and doors locked because they were afraid of crime, which meant the one thing that might have helped was the thing they would not do.
Heat is a social hazard as much as a physical one, and isolation is the risk factor that shows up again and again. Checking on an older neighbor during a heat stretch is a genuine intervention, not a courtesy. On the household side, a home that sheds heat and a plan for the hottest room are the substance of extreme heat preparation for any home, and the earliest signs of trouble are covered in survival hydration.