Who said the dog days of summer?

This year, while your summer plans may change due to COVID-19, the weather will still be hot. But what are the dog days of summer, and what do those days have to do with dogs?

“Sirius”-ly surprising origins

The phrase “dog days of summer” actually has nothing to do with man’s best friend. It turns out that the ancient Greeks and Romans weren’t referring to real dogs, but to the great astronomical one, Sirius. The “Dog Star” is located in the constellation Canis Major, known as the Greater Dog, and is the brightest star that shines at night.

Sirius is also known as “Nile Star” or “Star of Isis” because ancient Egyptians noticed 4,000 years ago that around the summer solstice, Sirius would appear to rise before dawn, which would be around the time when the Nile River would flood. Since ancient Egyptian life depended on agriculture, the flowing river would either bring great prosperity or great destruction. (Check out these fascinating facts about the summer solstice.)

Why “dog days of summer”?

What does the star Sirius have to do with the “dog days of summer”? According to the Farmer’s Alamanac, during summer months and specifically on July 23rd, Sirius is extraordinarily bright and, in certain parts of the world, rises and sets with the sun at that time. Ancient Romans believed this shining star contributed to the sun’s heat, thus referring to this extremely hot period as diēs caniculārēs, or “dog days.” The term evolved to mean the 20 days before and after July 23rd, or July 3 to August 11, to coincide with Sirius aligning with the sun. However, depending on where you are in the world, the astronomical dog days and the rising of Sirius vary.

You could also find references to the “dog days of summer” in ancient texts. “If you go back even as far as Homer, The Iliad, it’s referring to Sirius as Orion’s dog rising, and it describes the star as being associated with war and disaster,” Jay B. Holberg, author of Sirius: Brightest Diamond in the Night Sky and senior research scientist at the University of Arizona Lunar & Planetary Laboratory tells National Geographic. “All throughout Greek and Roman literature, you found these things.” The phrase “dog days” has since taken on various meanings after its translation from Latin to English. (These are the Latin words you use every day without knowing it!)

What does science have to do with it?

Even though Sirius is extremely bright, the extra heat is not because of any additional radiation from this star. The earth rotates around the sun and the Earth’s tilted axis is why we experience seasons. The sun is hotter in certain hemispheres because the sun’s rays hit the Earth in a more direct way due to Earth’s tilt. For example, if the North Pole is tilted toward the sun, that translates to hotter days in the Northern Hemisphere. Similarly, if the South Pole is tilted toward the sun, that means it’s winter in the Northern Hemisphere. However, stars shift, the earth wobbles, and the “dog days” of ancient Greece aren’t the same “dog days” of now, and the “dog days” of now won’t be the same as thousands of years from now.

How do you see Sirius?

To find Sirius in the night sky on winter evenings, locate the Orion constellation and then find Orion’s belt. Once you’ve located the three stars that make up Orion’s belt, move in a line down to the left until you find Sirius.

Here are the world’s most contagious myths and misconceptions—debunked.

Originally Published: July 03, 2020

The “Dog Days” of summer are from July 3 to August 11 each year. They’re usually the hottest and most unbearable days of the season. We often hear about the “Dog Days” of summer, but few know where the expression originated. Some think it’s a reference to the hot, sultry days that are “not fit for a dog.” Others suggest it’s the time of year when the extreme heat drives dogs mad. But where does the term come from? And what does it have to do with dogs? You may be surprised to see is has to do with the stars! Read on.

The “Dog Days” Expression Explained

The phrase is a reference to Sirius, the Dog Star. During the “Dog Days” period, the Sun occupies the same region of the sky as Sirius, the brightest star visible from any part of Earth. Sirius is a part of the constellation Canis Major, the Greater Dog.

In the summer, Sirius rises and sets with the Sun. On July 23rd, specifically, it is in conjunction with the Sun, and because the star is so bright, the ancient Romans believed it actually gave off heat and added to the Sun’s warmth, accounting for the long stretch of sultry weather. They referred to this time as diēs caniculārēs, or “dog days.”

Thus, the term Dog Days of Summer came to mean the 20 days before and 20 days after this alignment of Sirius with the Sun—July 3 to August 11 each year.

Summer heat is due to the Earth’s tilt

While this period usually is the hottest stretch of summer, the heat is not due to any added radiation from Sirius, regardless of its brightness. The heat of summer is simply a direct result of the Earth’s tilt.

During summer in the Northern Hemisphere, the tilt of the Earth causes the Sun’s rays to hit at a more direct angle, and for a longer period of time throughout the day. This means longer, hotter days.

What do the “Dog Days” of summer mean to you?

If you plan to take a vacation during this time, read some of our great ideas to stay cool:

Natural Ways To Keep Cool This Summer

Keep 15 Ways To Keep Your Pet Healthy and Hydrated in the Heat

6 Creative Ways To Keep Cool During Hot Summer Days

Cool Ways To Exercise Safely In Summer

What To Wear When The Temperature Soars

Thirsty? Drink This!

Can basil Seeds keep you cool?

The words "dog days of summer" might conjure up images of canines panting in the heat, but the origin of the phrase actually has to do with the stars.

Historians say the phrase dates back to the ancient Greeks and Romans, who would keep track of the seasons by looking up at the sky. The star Sirius was known as the "dog star" because it made up the nose of a constellation shaped like a dog.

But the ancient civilizations' predictions don't quite work for modern times, according to National Geographic. That's because the Earth's rotation wobbles, meaning Sirius does not appear in the sky at the same time of year as it did back then. The Farmer's Almanac lists the modern dog days as lasting 40 days from July 3- August 11.

Report a correction or typo