Borrego Sun - Since 1949

Dog Days of Summer


Last updated 9/7/2022 at 10:02am

Early astronomers noticed that, during the late summer, the brilliant star Sirius rose around the same time as the sun (its "heliacal rising," as we know it today), and the two moved across the daytime sky together.

As summers go, this one hasn't been unusually hot here in the Southern California desert, but it's not over yet! We've still got a while before the onset of autumn and, hopefully, the arrival of some cooler temperatures.

In the meantime, however, pay close attention and I'll bet you'll hear someone refer to this time of year as the "dog days of summer." One might guess that the term comes from the seemingly lethargic behavior of our canine companions in the late-summer heat, but then one would be barking up the wrong tree.

No, its origin – like that of many everyday phrases – lies among the stars.

The ancients, particularly the Romans and Greeks, knew late summer not only for its sweltering heat but also for the disease and discomfort that accompanied it. It was a time when meat spoiled rapidly, and food poisoning could become widespread.

Early sky watchers kept watch on the heavens to try to correlate terrestrial and celestial activity, and they noticed that, during this brutally hot season, the brilliant star Sirius rose around the same time as the sun (its "heliacal rising," as we know it today), and the two moved across the daytime sky together.

Sirius is well known as the "Dog Star" because it marks the constellation Canis Major, the Great Dog. And many in olden times believed that it was the heat of brilliant Sirius, coupled with that of the sun, that produced the scorching summertime temperatures – the "caniculares dies" or "dog days" as the Romans called them. Over time, the link between the late summer heat and the Dog Star – and the phrase "dog days" – became ingrained into popular culture.

Granted, Sirius is nearly twice as hot as our sun but, at a distance of some 51 trillion miles, the heat we receive from it is negligible. However, such ideas die hard; in fact, I wouldn't be surprised if some people still believe its connection today, despite it being debunked more than 20 centuries ago by the Greek astronomer Geminus:

"It is generally believed that Sirius produces the heat of the Dog Days," he wrote, "but this is an error, for the star merely marks a season of the year when the Sun's heat is the greatest."

Nowadays, if you wish to watch the heliacal rising of Sirius, you must do so in August. This is because the Earth wobbles on its axis – an effect called precession – and over several millennia, the positions of celestial objects shift slightly. But if we could see stars in broad daylight, we could now enjoy those of winter – including brilliant Sirius – shining all day long.

Of course, if you'd like to see Sirius in a dark sky, you'll have to wait a few months until the sun no longer appears in the same part of the sky. That occurs during the winter months and, when it does, Sirius will appear as a sparkling diamond rising in the east at sunset.

With or without Sirius in our sky, summertime is hot. So, enjoy the warmth while it lasts because, as sure as you're reading my words, we'll all soon be whining about the cold!

Visit Dennis Mammana at