This paper studies climate adaptation in the semi-arid regions of Brazil based on individual-level administrative data covering the near universe of disadvantaged households. We show that after a drought poorer households are more likely to migrate, have fewer children and die more, while less disadvantaged households migrate less, have fewer children but not more deaths. In this context, we analyze the impacts of a large-scale climate adaptation policy, which provided over a million poor households with domestic-use, rain-fed water tanks (cisterns). The provision of cisterns leads to a large decrease in mortality and migration among beneficiaries as compared to matched non-beneficiaries that had the same characteristics at baseline. Cistern receipt cuts by half the migration and mortality response to a drought among the poor. Our results indicate that public provision of a low-cost, in-place adaptation technology can save lives and improve welfare in contexts where the poor have limited climate adaptation strategies.