New York City may not sleep, but it sure sweats. Climate scientists at The City College of New York City predict that heat waves such as the ones last July may intensify in the future. Manhattan is already subject to a greater urban heat island effect than the suburbs and because of the density and heat-inducing surfaces. This means that the city cannot cool off as quickly and thus continues to amplify heat. Researchers suggest that landscapers and policymakers implement cooling tactics such as green roofs to mitigate the effects.
http://www.sciencedaily.com/releases/2010/07/100729101613.htm