July 13 is the anniversary of the hottest day of Chicago’s deadliest weather disaster. From July 12 through July 16, 1995, the city sat under heat and humidity the National Weather Service still describes as probably the most intense combination on record here. The official high at O’Hare on July 13 was 104°F, second only to the all-time record of 105°F on July 24, 1934. Midway reached 106°F. The heat index peaked at 119°F at O’Hare and 125°F at Midway. Dew points were in the upper 70s to around 80°F. The Weather Service counts 583 deaths.
The number is the reason to remember the week. A large share of those deaths were older adults who lived alone, in brick buildings, without a working air conditioner, on nights when the outdoor air never offered a reset. The urban heat island kept neighborhoods warm after dark. Opening a window did not produce a cool night. It produced more humid air.
Comfort is the wrong category
Central air and a solid window unit are comfort equipment in a normal July. In a week like 1995 they are safety equipment. The same is true, on a smaller scale, in any Chicago summer stretch with dew points in the 70s and nights that stay above 75°F. The body sheds heat poorly in that air. A house that stays in the 70s, with the moisture pulled down, is doing health work.
Equipment fails at the worst moment of a heat wave because that is when it runs the longest, often with a dirty coil and a low electrical supply as the whole region turns compressors on. A capacitor that was marginal in June quits on the third day of the heat. There is no same-day appointment left in the city. The repair that was available in May is a wait in July, and the wait is the dangerous part.
What to have done before the anniversary, not on it
Service the air conditioner in spring. Clean the outdoor coil, prove the condensate drain, and replace the parts that are already weak. Know a neighbor who lives alone and check on them when the overnight low stays high. If the only cooling is a window unit, confirm it actually cools the room where that person sleeps. If you have central air and a section of the house never gets there, fix the duct or the zoning before the holiday, not during it.
We wrote about the ordinary version of this wear in what a Chicago summer does to an air conditioner. The 1995 heat wave is the extraordinary version, and it is still the right measuring stick. Zima HVAC is in Mundelein and serves Lake County. Call (847) 323-8314 and put the cooling service on the calendar while the schedule can still keep you safe.