Summer smog may be getting worse because you can't take the heat, according to a study released today in the journal Environmental Science & Technology.

Researchers have long known that ozone—smog’s main ingredient—is incredibly sensitive to warmer temperatures, which speed up chemical reaction rates, alter weather patterns, and sometimes trap pollution in place. At the same time, we know intuitively that on hotter days we tend to turn our air conditioners up, using more electricity.

“But it had kind of been bothering me that nobody looked at how energy use on hot days also contributes to ozone,” said study author Tracey Holloway, a researcher at the Nelson Institute for Environmental Studies at the University of Wisconsin-Madison. “How do you control air pollution on the dirtiest days? And how much are our power plant emissions changing when we have those hot chemically reactive days?”