In 1896, during 10 terribly hot days in New York City--the city's heat index "routinely" surpassed 120 degrees--1300 people died from the heat.
Without air conditioning or even reliable deliveries of ice, tenements became ovenlike death traps. Almost the entire Lower East Side, around 250,000 people, scrambled up to their roofs to sleep. Those who failed to procure a spot on a sweltering roof were forced to sleep on fire escapes, windowsills and stoops. It was not uncommon to hear of people who rolled over in their sleep, falling to their death. One man even drowned after turning over -- his bed was a Hudson River pier at West 37th Street.
But the hellish heat itself was the main killer. City papers began reporting on a shortage of coffins. Overcrowded morgues had to lay bodies on the floor.