The unit on “Air and Water” groups cases in which particular emphasis is placed on aspects of the typical micro-climate or the freshwater resources in areas visited by the correspondents. Among other issues, the objective is to record these data and to examine how the epistolographers perceive and convey these fundamental elements of the physical environment. The cases to which he letters lead us are the island of Kerkyra (Corfu), the city of Larissa in Thessaly, an area in Central Greece by the name of Brontitze, and the island of Lesbos in the North Aegean. Views on the connection of fresh water and climate, especially a mild climate, with distinct differences between the seasons, and their role in agricultural production and human longevity are intertwined in the texts. The cases offer diverse examples of the way in which the Byzantine scholars perceive and convey these fundamental elements of the physical environment, and of how the local societies adapted their productive activities to the climatic particularities of the areas in which they lived.