The rain god was among the most important of the Aztec deities, governing the spheres of water, fertility, and agriculture. Tlaloc oversaw crop growth, especially maize, and the regular cycle of the seasons. He ruled over the 13-day sequence in the 260-day ritual calendar beginning with the day Ce Quiauitl (One Rain). Tlaloc's female consort was Chalchiuhtlicue (Jade Her Skirt) who presided over freshwater lakes and streams.
Archaeologists and historians suggest that the emphasis on this well-known god was a way for the Aztec rulers to legitimize their rule over the region. For this reason, they built a shrine to Tlaloc on the top of the Great Temple of Tenochtitlan, just next to the one dedicated to Huitzilopochtli, the Aztec patron deity.