Two climate-related health risks are converging with alarming frequency: record high temperatures, and air pollution from things like car exhaust and wildfire smoke. Separately, these conditions can make people acutely sick and exacerbate existing health problems. But what happens when they coincide?

Recently, researchers at the University of Southern California set out to answer that question. Their results, based on mortality data from California between 2014 and 2019 and published at…