Here is an interesting take on the tragedy that was the Chicago Heat Wave of '95. Mind you it was a wonderful summer compared to the French Heat Wave Debacle, but for an American tragedy it was pretty bad. The worst part is that the total number will never be known because some of the heat-related deaths occured after the heat wave, and so many of them could have been prevented. I live in the Mojave and we would never see anything this bad here. Different circumstances, of course, such as swamp coolers being effective here and people of all ages being better acclimated to the heat.
PS: No, 9/11 wasn't simply a tragedy, it was an attack. It was yet another act of war perpetrated on America by Islamaist bent on spreading Islam through it's traditional means of Jihad.