Over the past 40 years, the urbanization process has developed rapidly all over the world. This is especially so in China, where the urbanization rate has reached 59.58% in 2018, and more than 831.37 million people live in cities (X. Li et al., 2019). Rapid urbanization has introduced many adverse effects, such as urban heat islands (UHIs; Y. Chen & Zhang, 2018), heavier rainfall (Miao et al., 2011), storm floods (Ntelekos et al., 2010), and air pollution (Baklanov et al., 2016). The UHI effect, in which urban areas are hotter than their rural surroundings, results from absorption and retention of heat by the built environment, less vegetation cover, and abundant anthropogenic heat release in cities (Oke, 1982). The UHI effect has profound impacts on the urban environment, particularly on human thermal comfort and health (Kovats & Hajat, 2008). Heat waves, periods of abnormally hot weather, exacerbate the UHI effect and cause cities to be more vulnerable, resulting in higher heat stress for urban residents (Li & Bou-Zeid, 2013). In the Yangtze River Delta, UHI-enhanced heat waves have shown an increasing trend in recent years (Ao et al., 2019; Tan et al., 2010; Xia et al., 2016). The combination of UHI effects and heat waves is becoming an important issue in this area because of its hot summer season. To predict the effects of heat waves on human health, a heat stress index is often used (Buzan et al., 2015). Heat stress is a complex measure combining temperature, humidity, wind speed, and solar radiation, coupled with individual factors including age, metabolism, physical activity, and health (Willett & Sherwood, 2012). With rapid urbanization and global warming, the overall trend is toward increasing heat stress on humans