Across the world, desalinization, wastewater recycling, and rainwater collection are just a few of the new technological and social processes transforming human–water relations in urban areas. Although rainwater collection is an ancient technology, I argue that its formalization as a water conservation technology in American cities brings into being novel resources and subjectivities. By analyzing the implementation of rainwater collection systems in Tucson, Arizona, I explore how precipitation and urban residents become internally related through their situated engagements in a water conservation program. The analysis presented in this article draws on ethnographic insights from the everyday lived experiences of rainwater management in urban households as well as in policy analysis, landscape surveys, and semistructured interviews with rainwater harvesters, experts, and decision makers. I demonstrate how, despite their involvement in a state‐funded water conservation program, rainwater harvesters are engaging in a new economic relationship with water, not to maximize efficiency in a place of scarcity (i.e., to reduce their potable water consumption), but rather to self‐fashion themselves into what they understand to be ethical subjects in a place of scarcity. Through this case study, I thus begin to ethnographically sketch the new hydrosocial relations emerging as cities confront the dual challenges of urban growth and climate change.