I don't think nearly that high, Dead. The buildings of Manhattan are far, FAR stronger than both of thos cities. They would serve to contain alot of the blast and heat. If I remember correctly, H and N went up like matchsticks due to everything being built of bamboo/wood. That kind of flash fire wouldn't happen as rapidly in a modern city.
Good point. The bottom line is, they aren't the end of the world, Just EXTREAMLY bad.