The 1896 New York heat wave lasted 10 days and killed ~1500 people. And has just 2 short paragraphs in Wikipedia (https://en.wikipedia.org/wiki/1896_Eastern_North_America_hea...)

> "This was 10 days [with temperatures reaching] 90 degrees at street level and 90 percent humidity, with temperatures not even dropping at night,"

https://www.npr.org/2010/08/11/129127924/the-heat-wave-of-18...

It wasn't necessarily a wake-up call then. But it may have at least been the crisis that spurred one guy...