Demand for water is increasing as U.S. droughts are expected to get more frequent and intense. "Cloud seeding" is an 80-year-old technology that adds tiny particles—usually silver iodide crystals—to clouds to trigger rain or snow. But the benefits of this technology are unproven. Some states are using cloud seeding, but there is little federal involvement. This technology assessment looks at how policies might address challenges such as unavailable or unreliable data on effectiveness, unpredictable cloud conditions, which need to be favorable for cloud seeding, and uncertain safety of using silver iodide more widely.