"Hot summer nights limit our ability to cool off and recover from extremely hot summer days. This can lead to higher heat stress, disrupted sleep, and related health risks. Each summer, [major U.S. cities] currently experience an average of 27 unusually warm summer nights with a strong climate change influence, compared to one such night each summer during the 1970s." https://www.climatecentral.org/climate-matters/warm-summer-nights-us-cities