The Dog Days of Summer

Many of us use colloquial phrases without knowing their exact origin. For many years, I thought I knew what the dog days of summer meant. Since these days fell on the hottest days of the year, I figured that it was just a representation of the harsh conditions for dogs left to pant outside in the scorching heat. And while this could be a proper way to equate the meaning, I found that I was very wrong. Well kind of wrong.

While these are the hottest days of the year (July 3rd through August 11), the phrase has more to do with the date than the temperature. The phrase references the Sun’s proximity to Sirius. Not the satellite radio service but the brightest star visible from any part of Earth. Part of the Constellation Canis Major (the Greater Dog), Sirius rises and sets with the Sun during the summer (aligned on July 23rd).

Because of the star‘s brightness, the Ancient Romans believed that the star added to the Sun’s warmth during those summer days. They called these days (the 20 days before and 20 after the day of perfect alignment – July 23) diēs caniculārēs or dog days. The phrase has represented the insufferable heat of summer’s hottest days since the Hellenistic period. (from the death of Alexander the Great in 323 BC to the rise of Augustus in 31 BC) and was translated in English in the 1500s. 


Featured Image: Domestic Dog at the Teotihuacan, Mexico by Emőke Dénes – kindly granted by the author, CC BY-SA 4.0,

Sunset Image by Own Work

The Stars of Canis Major as they can be seen by the naked eye; lines have been added for clarity by Till Credner:, CC BY-SA 3.0,

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