This One Earth Research Article shows how residential socioeconomic and racial segregation, in part due to historic redlining and unequal investment in green spaces, has led to disparities in heat exposure in the United States. This is expected to worsen as the climate warms, highlighting the need fro climate mitigation and adaptation (SDG 13), with additional implications for improving climate resilient and equitable infrastructure in cities (SDG 11) and public health interventions to reduce heat exposure (SDG 3).