Heat waves hit heat islands hardest

Extreme summers like that of 2012 — which saw record temperatures in cities across the U.S. — may be atypical, but experts say they will return, especially as the planet warms under climate change. And as they do, cities will be especially vulnerable.

A new University of Wisconsin-Madison study details how extreme temperatures affect urban heat islands — densely built areas where heat-retaining asphalt, brick and concrete make things hotter than their nonurban surroundings.