Climate Central has assessed the impact of urban heat islands on temperatures across 65 major U.S. cities, which together house 50 million people, or 15% of the country’s population. While global warming due to human activities is a significant driver of rising temperatures, the design and characteristics of urban environments exacerbate this heat.

The analysis involved calculating an Urban Heat Island (UHI) index for each census block group within these cities to determine the additional heat generated by the built environment. The resulting maps reveal varying patterns of heat concentration: in some cities like Cincinnati, the heat is concentrated in the urban core, while in others like Houston, it is more widespread across developed areas.