Sirius and the Dog Days of Summer

Sirius Returns to the Morning Sky

Towards late summer, early risers in the Northern Hemisphere can once again spot Sirius—the brightest star in our night sky—returning to the pre-dawn horizon. For thousands of years, its annual reappearance has been tied to the hottest stretch of the year: the “dog days of summer.”

Each year, Sirius disappears for several weeks or months (depending on your location) when it’s lost in the Sun’s glare during the daytime. Its heliacal rising—the first pre-dawn appearance after this period of invisibility—marks its return.

Even in the brightening twilight, Sirius is hard to miss. Its dazzling light often flickers through red, green, yellow, and blue hues as it twinkles low on the horizon shortly before sunrise.

When and Where to Look?

Sirius’s heliacal rising is visible across the Northern Hemisphere, though the further north you are from the equator, the later its rising occurs. At high latitudes, the best viewing may not begin until late August or even September.

How to spot Sirius:

1. Look toward the southeastern horizon before dawn.
2. Locate Orion’s Belt—three stars in a short, straight line.
3. Follow the line of the Belt downward to the brilliant white star of Sirius in the constellation Canis Major, the “Greater Dog.”

Our Night Sky Map shows Sirius’s position, rise and set times, and visibility for any date and location. Search for “Sirius,” select your date from the calendar, and slide the play bar to find the best viewing time.

The Dog Star

Sirius—officially Alpha Canis Majoris—is about 8.6 light-years away and shines with an apparent magnitude of –1.46, making it the brightest star visible from Earth at night.

Astronomers classify Sirius as a binary system: the luminous Sirius A and its faint companion Sirius B, a white dwarf not visible to the naked eye. When people mention Sirius, they are usually referring to Sirius A.

Located at the heart of the constellation Canis Major, which is Latin for “greater dog,” Sirius is also known as the Dog Star. In myth, Sirius was often seen as Orion’s faithful hunting dog, following the great hunter across the sky.

Its name comes from the Greek Seirios, meaning “sparkling” or “scorching,” and the rising of Sirius was associated with the hottest time of the year.

The Dog Days of Summer

For some ancient cultures, the first sight of Sirius returning to the dawn sky signaled the most intense heat of the year. It was believed that this bright star added extra heat to the season, ushering in what became known as the “dog days.”

Ancient Egypt

In Egypt, around 3000–1000 BCE, the heliacal rising of Sirius, known as Sopdet, roughly coincided with the annual flooding of the Nile River, a vital event for agriculture.

They honored Sirius as a goddess, and her return in the sky was considered a blessing. The star was associated with fertility and renewal.

Sirius was integral to their calendar system, marking the start of the Egyptian New Year, which would have been around mid-July according to today’s Gregorian calendar.

Ancient Greece

By the 8th century BCE, Greek poets like Homer referenced the heat and misfortune associated with Sirius, which rose in late July, bringing with it the year’s hottest weather. This period was linked to extreme heat, drought, and illness.

The Greeks called this time kynádes hēmérai—“dog days”—after the Dog Star in the constellation Canis Major, mythically seen as Orion’s dog, following him across the sky. Depending on the source, the “dog days” referred to either the days before or after this rising.

Ancient Rome

The Romans inherited the idea, calling the period dies caniculares. Their “dog days” lasted from late July through most of August.

By the 1st century CE, writers such as Pliny the Elder and Virgil linked this period to the star Sirius. Like the ancient Greeks, the Romans believed that Sirius intensified the Sun’s heat, causing lethargy, fevers, and bad luck.

From Myth to Modern Day

Today, “dog days” still refers to the hottest part of summer, though the connection to Sirius’s return to the night sky has been lost over time.

According to the Old Farmers’ Almanac, the dog days run from July 3 to August 11, now falling before Sirius’s heliacal rising.

Due to calendar changes and the slow wobble of Earth’s axis (precession), we’ve lost the direct link to the star that inspired the phrase. For example, in Cairo, Egypt, the heliacal rising of Sirius is now in early August, several weeks later than when the ancient Egyptians observed it.

Even though Sirius may have disappeared from the modern meaning of the dog days of summer, it continues to shine prominently in our night sky—as it has for millennia.