The state of knowledge of the natural world among Jews in early seventh-century Palestine (i.e., on the eve of the Muslim conquest), as reflected in a number of compositions by the liturgical poet Eleazar berabbi Qillir, is investigated. The focus is on Qillir's description of the process by which rain is produced and reaches the earth, as found in part of his oeuvre for the festival of Shemini Atzeret. This description draws heavily on materials from the rabbinic literature (especially Bereshit Rabbah), which are in turn rooted in biblical ideas about hydrology and rainmaking. The conception of the origin of rain, as conceived in these two corpora, is reviewed and analyzed to provide the proper background for an evaluation of Qillir's presentation. Special attention is paid to the way in which the midrashic material is arranged in the piyyuṭ as a poetic narrative, exposing a number of logical inconsistencies inherent in it.