It’s hot. It’s muggy. That must mean it’s the Dog Days of Summer. Well, almost. Astronomically speaking, the “dog days” ended in mid-August, but in popular usage, the term is often applied to the final sultry days of summer.
The dog days were named after Sirius, the “dog star,” which rises and sets with the Sun from late July to about the middle of August. The term goes back to ancient Egypt, where Sirius played a pivotal role in daily Egyptian life. Its first morning appearance heralded the Egyptian new year, as well as the yearly flooding of the Nile River, and the Egyptians looked to Sirius for clues about the upcoming harvest. If Sirius was bright when it made its first morning appearance, it was thought to signal a bountiful harvest, but if the star looked red and hazy, a scarce harvest was thought to follow.
Sirius played such an important role in Egyptian culture that the priests, who were in charge of the calendar, watched for the star from their temples. At the temple of Isis-Hathor at Denderah there was a statue of Isis that was positioned so that the light from Sirius would fall on a jewel in the statue’s forehead. When the priests saw Sirius shining on the jewel for the first time that year, they would emerge from the temple and announce the arrival of the new year.
Ancient cultures also blamed the intense summer heat on Sirius, because it was prominent in the sky during the hottest time of the year. And, because Sirius rises nearly in conjunction with the Sun, ancient people thought the combination of two such bright stars must be generating the sweltering heat. Today we know that Sirius does not cause the heat, but just happens to be most visible during the hot summer months.