A form of harmful air pollution that often can't be plainly observed is now being tracked with a groundbreaking new tool developed by scientists that allows residents to see where it's coming from.

In Arizona and California, multiple locations hit 112 degrees Fahrenheit last week.

As climate change produces ever more heat waves, how many homes in the U.S. lack adequate cooling? Who's most vulnerable to lethal temperatures, and exactly where do they live? A researcher at the ...