You know how hot New York City is if you've spent a summer in Manhattan, but have you ever visualized it? Determined to figure out why cities are substantially warmer than their surrounding areas, web researcher Nickolay Lamm brought a thermal imaging camera to the city to get answers. He discovered what he was looking for—it's called the "urban heat island effect." 

Thanks to surfaces paved with concrete and asphalt and few trees around, cities end up becoming sweat-boxes during the warmer months. The abundance of buildings and billboards don't help much, either. Hey, at least the season is about to change.

[via Gothamist]