‘Sirius,’ in the costellation Canis Major
Despite the name, the dog days of summer have nothing to do with dogs. The association is entirely celestial, rooted in the prominence of Sirius, the Dog Star, and its link to the peak heat of summer.
Ancient civilizations noted that the hottest stretch of the year aligned with the heliacal rising of Sirius, the brightest star visible in the night sky and a part of the constellation Canis Major (the “Greater Dog”). Greeks and Romans believed that when Sirius rose with the sun, the combined influence intensified summer’s heat, contributing to drought, fevers, overall discomfort and yes, even madness in dogs. They named the period dies caniculares, or “the puppy days,” a reference to Sirius’ place in the constellation. Over time, the phrase evolved into the dog days, retaining its astronomical roots even as scientific understanding changed.
Today, the term simply refers to the hottest, most oppressive stretch of summer in the Northern Hemisphere. In the English-speaking world, the dates are typically fixed from July 3 through Aug. 11. Sirius is now visible later — according to the Farmer’s Almanac, people in Florida typically spot it around Aug. 13.