Spatial Analysis of Extreme Nighttime Heat Events, Social Vulnerability, and Environmental Social Injustice in Madison, Wisconsin

The intent of this study is to identify the potential impacts of extreme nighttime heat on different communities in Madison, Wisconsin, including identifying metrics of environmental social injustice. An urban heat island effect has been observed in Madison, Wisconsin with studies showing a spatial relationship between extreme heat, socioeconomic indicators, demographics, and built environment. To examine the spatial distribution of nighttime heat, temperature data from 150 stations around Madison were composited for extreme nighttime heat events, defined as 3 or more consecutive days when minimum nighttime temperatures at the Dane County Regional Airport remain above the 95th percentile. We remapped these temperature composites into Dane County census tracts using ArcGIS to facilitate analysis alongside social vulnerability factors defined by the CDC and the Wisconsin Department of Health Services (DHS). Correlations between the spatial distribution of extreme temperature and the spatial distribution of socioeconomic indicators, demographics, and built environments, indicate how the distribution of heat could exacerbate already-existing vulnerabilities in Madison. Correlations between the spatial distribution of extreme heat and racial and ethnic minority demographics were used to measure environmental social injustice. Results showed a strong correlation between the spatial distribution of maximum daytime and nighttime temperatures, implying that areas prone to extreme daytime heat are also likely to experience a lack of nighttime heat relief. The spatial distribution of extreme nighttime heat was correlated with impervious surface and socioeconomic indicators. Demographic variations in Madison were not highly correlated with the spatial distribution of heat, indicating that the spatial distribution of temperature does not exacerbate already-existing heat impacts on racial and ethnic minority groups. The efforts of this exploratory study in Madison, Wisconsin, provide potential metrics for understanding and assessing the disproportionate effects of heat in other urban communities.