Advances in climate science reveal sharp variation in climate vulnerability within cities, yet most causal evidence relies on aggregated exposure measures across cities or larger regions. We combine high-resolution satellite data and administrative death records from Rio de Janeiro to estimate heat effects at the neighborhood level. Nearly 60% of excess elderly mortality is driven by localized exposure differences. As temperatures rise and spatial variation declines, city-wide shocks become more dominant. Preventive care and proximity to emergency services attenuate mortality, but only emergency access remains protective under localized exposure. Effective points of intervention may thus lie hidden within city-level averages.
