According to the standard narrative of the outcome of Valens's First Gothic War, the Goths sued for peace after being subjected to three years of conflict. Yet not only did the Romans fail to engage the Goths in a major battle, but they were also prevented from campaigning in Gothia during the second year of the war due to flooding of the Danube River. This article argues that the natural disaster described by Ammianus played a significant, and hitherto unexplored, role in compelling the Goths to surrender. It demonstrates how the hydroclimatological conditions that cause floods on the Lower Danube also tend to cause equally devastating flood events in other rivers that flowed through Gothia, thereby potentially wreaking havoc on Gothic territory that had remained unscathed by Roman raiding. It further utilizes Western and Central European dendroclimatological proxy evidence to show that the spring months of both 368 and 369 were among the wettest of the entire century, which provides corroboration for Ammianus's account and raises the possibility of additional flooding in the final year of the war. Finally, the article explores the ways in which flooding could have had deleterious impacts on the Gothic agrarian economy and their war effort.