Reminds me of the opening to "Ministry for the Future" by Kim Stanley Robinson.
In that book, a wet bulb event (high humidity and high temp) in India pushes infrastructure past the breaking point, the grid goes down, AC systems still running on generators are overloaded and overcrowded and fail, the water temp goes over body temp, and millions die.
The positive cultural/societal reaction to the disaster strained my suspension of disbelief pretty hard, as is typical of KSR novels in my experience, but the idea of a heat wave causing a massive catastrophe (and the poignant description of attempting to live through it) stuck with me.
I was also going to mention wet bulb temperatures as well. As horrible as the conditions described in the article is, it describes a very dry heat. Which means sweating and water can still help.
The really scary thing will be when the wet bulb temperature goes above 35 degrees, and humans can only survive with AC.
I don't believe I have heard of KSR before, but I have been telling my friends that an incident like this is in our (the world's) future.
It is feeling more and more imminent with each passing year.
And then there will be cries of nobody saw this coming.