Farm Progress

Weather Wise: Here’s a look at where that phrase may have originated.

Andy Eggert

July 11, 2017

2 Min Read
SUMMERTIME SKY: It turns out the dog days have nothing to do with the hot weather and are actually named after a star.Thinkstock

Where did the expression “dog days of summer” come from? How do you describe these types of days? What causes them to develop? Inquiring minds want to know!

This month’s Weather Wise column shifts the focus from the weather to the stars. The phrase “dog days of summer” is commonly thought to be about the late-summer heat that bogs down even the most energetic of dogs. While this explanation is quite reasonable and makes sense, it isn’t correct. The phrase dates to the ancient Greeks! You could probably win some friendly wagers on this one!

National Geographic claims in an article published online this summer that the Greeks named the late summer for the time of the year when Sirius, the dog star, rose in the sky just before the sun. In ancient times, this occurred in late July, and coincided with the hottest times of the summer. 

The Greeks believed this period would bring fever, war or some other catastrophe. In Homer’s epic “The Iliad,” Sirius is called Orion’s dog, in reference to nearby constellations of the summertime sky in the Northern Hemisphere. 

Jay Holberg of the University of Arizona states that references to the dog days and disaster are found throughout ancient Greek and Roman literature. The phrase made its way into English usage approximately 500 years ago and has evolved ever since.

Dog days today
While the dog days of summer currently still align reasonably well with the hottest days of the year in the Northern Hemisphere, that may not always be the case. As time passes, the Earth’s axis shifts in relation to the stars, in a process called precession.

The time of year the Greeks called the dog days has shifted in relation to the calendar we use. Already, the dog days don’t align with the exact same time of year that they once did. 

In about 13,000 years, the solar dog days will occur in midwinter, and the North Star will have a very inaccurate name.

Somehow the dog days of winter just doesn’t have the same ring to it!

Eggert works in the Indiana State Climate Office and writes from West Lafayette.

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