The Dog Days of Summer: Less About Hot Dogs and More About Astronomy

Do dogs get lazier in the heat of summer. Source: (fineartamerica.com)

When the heat of July hits like a blanket fresh from the dryer, the old-timers like to say that we are in the dog days of summer. If you are like most people, this conjures up images of lazy dogs—for some reason, it is a Bassett Hound in my vision—reclined on the front porch, panting away the heat. While it may be true that some dogs are less active in the oppressing heat, that's not how the phrase "dog days of summer" started. To find the origins of this phrase, we have to look not to the front porch but into the night sky. 

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The brightest star in the sky is Sirius, the Dog Star. Source: (humanoriginproject.com)

It's All About Sirius ... Seriously

It was the ancient Greeks and Romans who first coined the phrase "dog days of summer." For them, this was a term to describe the period of time in the summer when Sirius, the so-called "dog star," rises in the early morning sky just before the sunrise. Sirius is visible from early July through the end of August, so its appearance coincides with the hottest time of the summer. The ancient Romans believed that Sirius was so bright that it send its heat to Earth, just like the Sun does, and caused July and August to be extra hot and steamy. 

Sirius is located in the constellation Canis Major, or Large Dog. Source: (astronomytrek.com)

The Dog Star

The dog star, Sirius, is the brightest star in the night sky. It is located in the constellation known as Canis Major, which translates to "large dog." Finding the dog star in the sky is fairly easy. After all, it is the brightest star. But the three stars of Orion's belt also point directly to Sirius. In fact, in many myths, Canis Major is referred to as Orion's dog. Just look how cute it is!

The Dog Days meant disaster for ancient Romans. Source: (rome.net)

A Back Luck Star

For ancient cultures without air conditioning and popsicles, the sweltering summer days were torture. During the dog days of summer, diseases spread, storms rages, food spoiled, and livestock withered away. The appearance of Sirius was often associated with back luck, sickness, and natural disasters. In The Iliad by Homer, the author connects the rise of Sirius with impending war and catastrophe. 

A group of seven mixed breed dogs take over a wooden porch to relax in the sunshine during the dog days of summer. Source: (Photo by Kirn Vintage Stock/Corbis via Getty Images)

A Shift in the Dog Days?

The night sky has changed slightly since ancient times, and the Earth has shifted position as well. The Romans understood the dog days to be from around July 20 until August 24. The current edition of The Old Farmer's Almanac, however, shows the days as occurring between July 3 and August 10. The discrepancy can be explained by the shifting of the constellations, the rotation of the Earth, and more importantly, by the location of Rome, which lies closer to the equator than the United States. This year, the dog star will not rise over Rome and Athens until the middle of August. 

Eventually, the dog days may be in mid-winter. Until that time, humans and dogs need to find the best way to cool off in the dog days of summer. Source: (barraques.com)

The Dog Days of Winter?

The shift is gradual, but it is clear that the rise of Sirius, signaling the start of the dog days of summer, is occurring later and later in our calendar year. Astronomers theorize that in several thousand years, the dog star will have shifted so much that the rise of Sirius will happen in the middle of winter, and I guess I'll start needing to really focus on conjuring up images of Huskies instead of Basset Hounds.