Hibernation the summer months is aestivation. Often associated with low temperatures, the function of hibernation is to conserve energy when sufficient food is unavailable. To achieve this energy saving, an endothermic animal decreases its metabolic rate and thereby its body temperature. Hibernation may last days, weeks, or months depending on the species, ambient temperature, time of year, and the individual's body condition. Before entering hibernation, animals need to store enough energy to last through the duration of their dormant period, possibly as long as the entire winter. Larger species become hyperphagic, eating a large amount of food and storing the energy
Season of the Emergence known as Winter. In the lunar calendar, the intercalary month was added as needed to maintain the heliacal rising of Sirius in the fourth month of the season of the Harvest. This meant that the Season of the Emergence usually lasted from January to May. Because the precise timing of the flood varied, the months of "Emergence" no longer precisely reflected the state of the river but the season was usually the time for the planting and growth of Egyptian grain. In the civil calendar, the lack of leap years into the Ptolemaic and Roman periods meant the season lost