Sirius before dawn Photo | Alan Sealls
If you have a dog, every day is a dog day. Dog or not, the long, hot, humid August days we survived are often called the dog days of summer. What has that to do with dogs? Not much, directly. The phrase’s origin is astronomical, not meteorological. Meteorology is the day-to-day weather changes in Earth’s atmosphere. Astronomy is far outside of the atmosphere. In fact, it’s above my head! People always ask me questions about it, so I did a little research.
August is when the constellation Canis Major appears in the predawn eastern sky. Canis Major translates to “big dog.” That constellation features the brightest and most obvious star, Sirius, nicknamed Dog Star. Ancient Romans saw the star as an evil omen, as they associated it with disease and calamity. My guess is the negative impacts attributed to Sirius were from the summer heat.
Depending on what almanac or reference book you check, you’ll find different dates for dog days. From the Library of Congress, I perused South Carolina’s Yorkville Enquirer from August 17, 1898. The paper’s “Miscellaneous Reading” column stated, “The subject of dog days is a very interesting one at this time of the year, and there are many opinions as to when dog days really begin, when they end and what they are. Some people hold that dog days do not begin until August 1st, while others contend that they begin on July 28th.” Like many things of folklore and legend, there is no real boundary or measurement.
Toward daybreak, even now, as the sky slowly brightens, it becomes harder to see the Canis Major constellation. As long as the sky is clear, you can easily spot Sirius. With Sirius fairly close to the horizon, you see it through a thicker amount of air than when it’s high in the sky. The heat radiated from Earth through the atmosphere to space fluctuates and causes the path of light to fluctuate too. That’s what causes stars to shimmer or scintillate. It’s the same effect you notice at night when you look at lights across Mobile Bay, at distant lights offshore or even at distant city lights. They dance and shimmer.
The dog days are also coincident with a regular increase in tropical storms and hurricanes. Credit that increase to the large quantity of heat the ocean absorbs all summer to support tropical tempests. That’s also why just about every week you’ll recall an anniversary of some notable hurricane.
In fairness to dogs, maybe after the dog days, we can say we are in the cat days … Cat 1, Cat 2, Cat 3 … doggonit!
Alan Sealls is chief meteorologist at NBC15 and an adjunct meteorology professor at the University of South Alabama.
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