The phrase “dogs days of summer” comes from the positioning of the celestial bodies in the northern hemisphere. In the beginning of the month of July, Sirius, the dog star, begins to rise and set in the same position of the sky as the sun, according to Farmer’s Almanac. At this time of year, the sun’s location also happens to coincide with the constellation Canis Major, the Greater Dog. Because of the sun’s proximity to these canine-themed stars, the ancient Romans began referring to this time of year as “diēs caniculārēs,” which translates into “dog days.”
The “dog days” are characterized as being the hottest and most stifling days of the year. Ancient civilizations believed that Sirius, which is the brightest star in the sky visible from the earth, was to blame for the oppressive weather. Since it was so bright, ancient Romans believed that the reason that the temperature on earth rose so much during those months was because Sirius was throwing off its own heat. However, we now know that Sirius’ position in the sky has nothing to do with hot summer weather, which is caused simply by the position of the earth’s tilt.