The main geographic and socioeconomic characteristics of the La Plata Basin are described, along with an overview of its prevailing climate. Two major climatic zones within the basin are identified: a tropical portion in the north and a subtropical portion in the south, the latter corresponding to the region commonly referred to in the literature as Southeastern South America (SESA). The book aims to present current and updated knowledge on climate variability in the basin in a manner that is accessible to professionals who are not experts in climate science but work in technical fields related to socioeconomic sectors within the basin—such as water resources, agriculture, energy, health —or are involved in the research and management of natural assets tied to ecosystems and biodiversity.