Local Changes in Urban Heat Vulnerability During Extreme Summer Weather

Global climate change is increasing the intensity and frequency of extreme heat events, which already claim more lives each year than all other weather related disasters combined. Urban populations are particularly vulnerable to health impacts of excessive heat because of the concentration of vulnerable populations and the tendency of built environments to influence local temperatures. To explain how patterns of vulnerability vary within urban areas and how extreme weather events might influence this vulnerability, we empirically examine the distribution of social, thermal, and physical metrics across the built environment under normal and extreme summer conditions from 2006. Using apparent minimum temperature thresholds and daily measurements from the National Climatic Data Center, we identified periods of normal and extreme summer heat conditions for Atlanta, Chicago, and Philadelphia. Land surface temperatures from Landsat Thematic Mapper satellite imagery were combined with published risk factors for heat morality obtained from the 2010 American Community Survey. The resulting descriptions of potential heat-related health impacts during normal and extreme summer weather were compared to identify how vulnerability changes with extreme summer heat. We used spatial statistics to assess the clustering of high risk areas under both types of summer conditions as well as to assess the relationship between modifiable built environment variables and land surface temperatures. We find that the association of built environment variables, including impervious surfaces, to be emphasized during extreme summer weather and urban vulnerability to change, by varying degrees between cities, with the presentation of potentially hazardous meteorology. The results of this work emphasize the importance of localized descriptions for preventing and responding to heat-related hazards.