Heat islands raise temps for most Philadelphians

As dangerously high temps hit Philadelphia and the U.S. this summer, a new analysis finds urban "heat islands" significantly exacerbate such extreme weather.

Why it matters: More than half of Philadelphians live in heat islands — hotspots with higher temperatures compared to surrounding areas, according to Climate Central .

• That can make parts of the city feel unlivable during heat waves , which are getting longer and more frequent in the region.

The big picture: Urban heat islands (UHIs) are boosting temperatures within 65 major U.S. cities that are home to 50 million people, or 15% of the total U.S. population, per Climate Central's analysis.

• Nearly 34 million, or 68% of those people, were found to live in environments where UHIs were capable of boosting temps by at least 8°F.

How it works: Heat islands are created when roads, buildings, parking lots and so on "trap" heat.

State of play: In Philadelphia, 52% of the population lives on blocks where heat islands make temps feel an average of 8.1° hotter.

• Meanwhile, 16% live where it feels at least 10% hotter than average temps.

Between the lines: Low-income neighborhoods in Philly tend to be hotter due to fewer trees and green spaces while also being exposed to more asphalt surfaces.

Zoom out: U.S. cities in the Climate Central analysis whose citywide UHI effects can increase temperatures the most include New York (9.6°), San Francisco (9.1°), and Newark, New Jersey (9°).

Caveat: Scientists factor the heat island effect into their climate change monitoring and projections, and it does not explain the sharp uptick in global average temperatures , melting glaciers , record ocean warmth and more.

What they're saying: "The entire planet is warming due to human-caused climate change, but the built environment further amplifies both average temperatures and extreme heat in cities," per a Climate Central statement announcing the new data.

What we're watching: This summer has already seen several prolonged heat waves (like last week's), and one of its warmest Junes on record — holding true predictions for an unusually hot season .