For many Americans, managing high summer temperatures has become a fact of life. Unfortunately, the human toll of these longer and more intense heat waves is also increasing.
Heat waves — defined by the National Oceanic and Atmospheric Administration as periods of two or more days where the weather is “abnormally and uncomfortably hot” and “outside the historical averages for a given area”[1] — have become more frequent and longer in duration since the middle of the 20th century. In April 2023, 69.7 million Americans lived in counties experiencing higher temperatures than the 20th-century normal.
