Do microclimates matter? The health impacts of urban heat using fine-scale data

Abstract

Cities tend to be warmer than their suburban counterparts, a phenomenon known as the heat island effect. This effect varies significantly over time and across different neighborhoods. This study examines the health implications of neighborhood-level temperature variations and the role of urban heat in the temperature–health relationship. Using high-resolution satellite-derived surface temperature data and emergency medical service records from Northern California, the analysis employs fixed-effects Poisson regressions. The findings show that neighborhood-level extreme heat has significant adverse health effects. However, urban heat—a highly localized and predominantly anthropogenic component of overall temperature—is less harmful than temperature shifts on a larger geographic scale. This is likely because people can better adapt to urban heat. These results highlight the importance of considering both overall temperature exposure and adaptation potential in urban environments. The effects of urban heat also vary by season. While additional warmth can provide protection during colder periods, it poses substantial health risks on warmer days. Finally, policy simulations suggest that mitigating extreme urban heat could effectively reduce health risks, particularly during warm periods. Tree planting, especially in less vegetated areas, is a beneficial strategy for protecting urban populations.