The Dog Days of Summer

What and When are the Dog Days of Summer?

July 24, 2019

What are the “Dog Days of Summer”—and when are they? The origin of this common phrase might surprise you. Enjoy this page about the meaning and origins of the “Dog Days of Summer.”

What Are the Dog Days of Summer?

The Dog Days aren’t just when your dog starts panting on a hot summer day.

These days once coincided with the year’s heliacal (meaning “at sunrise”) rising of the Dog Star, Sirius.  

Ancient folks thought that the “combined heat” of Sirius and the Sun caused midsummer’s sweltering weather.

Of course, the appearance of Sirius does not actually affect the weather, but for the ancient Egyptians, Sirius came into view just before the Nile River’s flood season. They used Sirius as a “watchdog” for that event. Because it also coincided with a time of extreme heat, the connection with hot, sultry weather was made for all of time!

When Are the Dog Days of Summer?

According to The Old Farmer’s Almanac, the Dog Days of summer are traditionally the 40 days beginning July 3 and ending August 11, which coincide with the dawn rising of Sirius, the Dog Star. This is soon after the Summer Solstice, which of course also indicates that the worst summer heat will soon set in.

The Dog Star, Sirius

The Old Farmer’s Almanac for Kids tells us all about the Dog Star, Sirius! Here are some of the most important facts:

Sirius is the brightest star in the sky, if you don’t count the Sun. Under the right conditions, it can even be seen with the naked eye during the day. Sirius is one star in a group of stars that form the constellation Canis Major, meaning “Greater Dog.” It’s no surprise, then, that the nickname of this big, bold star is Dog Star. Learn how to find the Dog Star in the night sky.


Sirius in Ancient Egypt

In ancient Egypt, the Nile River flooded each year, usually beginning in late June. The people welcomed this event, called the Inundation, because the floodwaters brought rich soil needed to grow crops in what was otherwise a desert. 

No one in Egypt knew exactly when the flooding would start, but they noticed a coincidence that gave them a clue: The water began to rise on the days when Sirius began to rise before the Sun. They called Sirius SOTHISSOTHIS and the Inundation became so important to the Egyptians’ survival that they began their new year with the new Moon that followed the star’s first appearance on the eastern horizon.


A Time of Ill Fortune?

Unlike the Egyptians, the ancient Greeks and Romans were not pleased by Sirius’s appearance. For them, Sirius signaled a time when evil was brought to their lands with drought, disease, and discomfort.

Some people believed that the summer swelter was due to the combined heat from Sirius and the Sun. It makes sense that the name of the Dog Star, Sirius, means “scorching” in Greek.

Sirius was described as a “bringer of drought and plague to frail mortals, rises and saddens the sky with sinister light” by the Roman poet Virgil.

Is this just superstition? A 2009 Finnish study tested the traditional claim that the rate of infections is higher during the dog days. The authors wrote, “This study was conducted in order to challenge the myth that the rate of infections is higher during the dog days. To our surprise, the myth was found to be true.”


The Meaning of the Dog Star Today

Due to a very slow wobble of Earth’s axis, the Dog Star now seems to rise later than it did in ancient times. Its ascension no longer coincides with the start of the Nile flood (which does not occur anyway, because the river is now controlled by the Aswan Dam), but Sirius still makes its appearance during hot summer days. 

Dog Days of Summer Folklore

Old-timers believed that rainfall on the Dog Days was a bad omen, as foretold in this verse:
Dog Days bright and clear
Indicate a happy year;
But when accompanied by rain,
For better times, our hopes are vain.

Dog Days are approaching; you must, therefore, make both hay and haste while the Sun shines, for when old Sirius takes command of the weather, he is such an unsteady, crazy dog, there is no dependence upon him.
The Old Farmer’s Almanac, 1817

Watch our video on the Dog Days and the Dog Star! Plus, try this Dog-Days Iced Tea to keep you refreshed in the heat.


Reader Comments

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Dog days

For most of my childhood I have often been told that snakes bite more during dog days. My dad told us that the snakes eyes have a cloudy covering over them during the 'dog days'. Is there any scientific evidence of this ?

snake eyes

When snakes are about to shed their skin in summer, their eyes cloud over as the old eye covering layer is replaced with a new one. The eyes look milky in color and the snake’s vision is impaired until it sheds the old layer, usually a few days. This happens in summer, but not necessarily during the Dog Days.

Note, too that shedding can vary from species to species, as well as environmental conditions, the animal’s nutrition and their growth rate.

Dog days

Dog days of summer .. oh how i loathe thee.

My rooster not crowing and staying on perch

Weve had hard rains and very hot weather now my rooster is staying on perch not eating and not crowing. Do they do this during dog days

rooster troubles

Roosters and chickens can get heat stress, some signs being panting, lethargy, loss of appetite, holding their wings out. Make sure that your rooster has shelter/shade from the heat and plenty of water. Also check if he might be suffering from an illness. Hope this helps!


A bigger mystery to me is why August 17th is designated as the start of "Cat Days" in the almanac and always has been. What the heck are "cat days"?

Robins in July

On my walk around the track this morning I notice pairs of robins; one track the other, than flying very fast after the one it was stalking.
How can you tell the difference between a male and a female robin?

Cat Nights

“Cat Nights” harks back to a rather obscure old Irish legend concerning witches and the belief that a witch could turn herself into a cat eight times, but on the ninth time (August 17), she couldn’t regain her human form. This bit of folklore also gives us the saying, “A cat has nine lives.” Because August is a yowly time for cats, this may have prompted the speculation about witches on the prowl in the first place.