Extreme heat is among the leading causes of weather-related deaths in the US. Electrically-powered air conditioning can reduce heat exposure and thus protect human health. Due to rising demand and more frequent severe weather, electrical blackouts have become increasingly common. More frequent and intense heat waves are expected with climate change, so future blackouts may result in significant risks to public health, especially among children, the elderly, and the poor. Being prepared for blackout emergencies and reducing hazards may have important health benefits during heat waves. This research estimates the human health risk of concurrent heat wave and blackout events in the cities of Atlanta, Detroit, and Phoenix and examines the potential benefits of specific actions to reduce the impacts of extreme heat, including environmental changes, technological improvements, and behavioral changes. Models of regional climate, building interior heat exposure, and human health effects combine to simulate human heat exposure under heat wave and electrical grid blackout scenarios, quantify heat-related illness, and evaluate the potential for individual and institutional adaptive strategies to lessen the impacts of extreme heat. This project estimates the human health risk of blackouts during periods of extreme heat, which already take a heavy toll on public health. The outcomes of this research advances the progress of science through the development of a new approach to measuring indoor heat exposure and enhances national health through the testing of electrical generation, passive cooling, and behavioral adaptations to protect health during extreme weather hazards. This research further supports the development of new protocols for emergency response planning pertaining to heat risk monitoring and evacuation.