"That's the highest temperature I've seen on roofs," Columbia University's Stuart Gaffin said.
Heat Wave Blankets Much of U.S., Threatens Grids
But just a few feet away in some plants, it's a relatively cool 110. That's a result of what's called the urban heat island effect, when everything from buildings to sidewalks to rooftops and roads absorb the sun's heat and trap it, CBS News Correspondent Elaine Quijano reports.
Then there's the added heat generated by traffic, air conditioners and even people's own body heat. Without adequate green space to help cool the atmosphere, highly populated urban areas essentially become their own overheated micro-climates.
"It's completely manmade," said Gaffin. "It's the way we've transformed the landscape in cities, transformed it about as profoundly as you can from a natural environment."
In New York, the overnight low was 77 degrees while an hour away it was a cool 60. Boston was 74 while suburban Andover, Mass., was 61. Washington, D.C., dipped to 77 while nearby Alexandria, Va., dropped to 69.
"As we talk about vegetation, it drops dramatically," Gaffin said.
Gaffin and his students are studying the cooling effects of planting on rooftops.
"With green roofs we've discovered the equivalent of the street tree," Gaffin said.
After nearly a decade of research, he believes it's possible to undo what man has done.
"These surfaces are just sitting there waiting to harbor vegetation and do their job," Gaffin said.
In Times Square and other places around New York City, Gaffin says there's enough roof space where gardens could do the work of more than 20 tree-filled Central Parks, which could make a difference on a day like Tuesday.