The Dog Days of Summer, also known as Canicular Days, are typically the hottest and most unhealthy days of the year. The traditional timing of Dog Days is the 40 days beginning July 3rd and ending August 11th coinciding with the heliacal (at sunrise) rising of Sirius. Sirius, the Dog Star, is visible with the rising Sun at this time of year. Ancients associated this sky picture with the hot days that coincided with it. Sirius is the brightest star in the constellation Canis Major (Greater Dog).