Why Is It Called the 'Dog Days of Summer'? The Surprisingly Un-Doggy Origin Story

Published August 2026 · Pet N Pet Editorial · National Dog Day Science Series

The phrase has nothing to do with actual dogs panting through August. "Dog days of summer" comes from Sirius, the brightest star in the night sky, nicknamed the Dog Star because it sits in the constellation Canis Major, the Greater Dog. Ancient Greek and Roman astronomers noticed Sirius rises and sets with the sun during the hottest stretch of summer, and they blamed the star itself for the heat (National Weather Service).

The modern date range most commonly cited runs July 3 to August 11, twenty days on either side of Sirius's July 23 conjunction with the sun. The Romans called the period dies caniculares, "days of the little dog." Here's where the phrase actually comes from, what ancient writers really said about it, and whether it has anything to do with National Dog Day a couple of weeks later.

So Why Is It Named After Dogs?

The name traces to Sirius, part of the constellation Canis Major, Latin for "Greater Dog," which is why the star itself picked up the nickname "Dog Star." Ancient astronomers observed that Sirius becomes visible rising just before the sun during the hottest weeks of summer, a heliacal rising, and concluded the star's light was adding to the sun's heat (National Weather Service).

That belief turned out to be wrong. Modern meteorology attributes summer heat to Earth's axial tilt and thermal lag in the oceans and atmosphere, not any additional heat from a star 8.6 light-years away (NASA Astronomy Picture of the Day; Farmers' Almanac). But the name stuck around for roughly 2,000 years anyway.

What the Romans Actually Called It

The Romans used the Latin term dies caniculares, "days of the little dog," referring to Sirius by its diminutive nickname canicula. The Greek writer Plutarch reportedly used a similar phrase, hēmerai kynades, "dog days," around the same era (Merriam-Webster).

Ancient Writers Took the Dog Days Seriously, and Ominously

Homer wrote about it directly in the Iliad, comparing the warrior Achilles to Sirius: "brightest of all is he, yet withal is he a sign of evil, and bringeth much fever upon wretched mortals" (Book 22, trans. A.T. Murray, 1924). Centuries earlier, the poet Hesiod described the same star as something that "dries up the head and the knees" as "the skin is parched by the burning heat" (Works and Days, lines 582-588).

Pliny the Elder went further in his Natural History, writing that "the heat of the sun increases at the rising of the Lesser Dog-star" and that during this period, "dogs throughout the whole of that period are specially liable to rabies," a real belief that shaped how ancient communities treated dogs during the hottest weeks of the year.

The Greek poet Alcaeus, writing in the 7th or 6th century BC, took a more practical approach to the whole ordeal: "Wet your whistle, have some wine! Soon Sirius will rise and shine; the weather's bad..." (fragment 347, trans. Chris Childers). If the star was going to ruin your summer either way, you might as well have a drink about it.

Does This Have Anything to Do With National Dog Day?

Not really, though the timing is close. The traditional dog days run through August 11, and National Dog Day falls on August 26, about two weeks later. National Dog Day was founded in 2004 by pet lifestyle expert Colleen Paige for a personal reason unrelated to Sirius or Roman astronomy (nationaldogday.com). The overlap is a coincidence of the late-summer calendar, not a shared origin.

It's a tidy bit of timing anyway. The ancient world's unlucky dog-star days wind down in mid-August, and the actual dogs get their own, much friendlier holiday a couple of weeks after.

Frequently Asked Questions

What are the exact dates of the 'dog days of summer'?

The most commonly cited range is July 3 to August 11, twenty days before and after Sirius's July 23 conjunction with the sun, according to the National Weather Service. Some historical English calendars used slightly different ranges, but this is the modern standard.

Why is Sirius called the 'Dog Star'?

Sirius is the brightest star in the constellation Canis Major, Latin for 'Greater Dog,' which gave the star its nickname. Ancient astronomers noticed it rises just before the sun during the hottest stretch of summer and linked it to the heat, giving us both the star's nickname and the 'dog days' phrase.

Did ancient people really think a star caused the summer heat?

Yes. The Roman writer Pliny the Elder wrote that 'the heat of the sun increases at the rising of the Lesser Dog-star,' and Homer described Sirius as 'a sign of evil' that brings fever. Modern science attributes summer heat to Earth's axial tilt and thermal lag instead, but the ancient belief shaped the phrase we still use today.

Is 'dog days of summer' related to National Dog Day?

Not directly. The traditional dog days end around August 11, while National Dog Day falls on August 26, roughly two weeks later. National Dog Day's date was chosen by founder Colleen Paige for an unrelated personal reason, so the overlap is coincidental.

What does 'dies caniculares' mean?

It's Latin for 'days of the little dog,' referring to Sirius by its diminutive Latin nickname, canicula. It's the direct root of the English phrase 'dog days,' and the Greek writer Plutarch reportedly used a similar phrase, hēmerai kynades, around the same era.

Bottom Line

The "dog days of summer" were never about dogs panting in the heat. They're a roughly 2,000-year-old astronomy mistake, credited to Sirius, the Dog Star, that stuck around long after we figured out what actually causes summer heat. Ancient writers took it seriously enough to blame the star for fever, madness, and even rabies. Modern science knows better, but the name never changed.

SOURCES & CITATIONS

National Weather Service  "Dog days" date range (July 3-Aug 11) and origin in the Roman Empire.  https://www.weather.gov/wrn/summer-article-keep-your-pets-cool

Old Farmer's Almanac  Confirms the July 3-Aug 11 range and dies caniculares etymology (published July 3, 2026).  https://www.almanac.com/content/what-are-dog-days-summer

Farmers' Almanac  Modern scientific explanation for summer heat (Earth's axial tilt, thermal lag), updated July 21, 2026.  https://www.farmersalmanac.com/why-are-they-called-dog-days-of-summer

Merriam-Webster  Etymology of 'dog days' from Latin dies caniculares; Plutarch's Greek equivalent (partial verification, see Data Integrity note).  https://www.merriam-webster.com/dictionary/dog%20days

Perseus Digital Library, Tufts University  Homer, Iliad Book 22 (trans. A.T. Murray, 1924)  the Sirius/Achilles comparison.  https://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A1999.01.0134%3Abook%3D22%3Acard%3D1

Laurence Totelin, Cardiff University (The Recipes Project)  Hesiod, Works and Days, and Pliny the Elder's rabies/dog-days passages.  https://recipes.hypotheses.org/11610

attalus.org  Pliny the Elder, Natural History, Book II Ch. 40  full translated passage on Sirius and summer heat.  https://www.attalus.org/translate/pliny_hn2b.html

Literary Matters (trans. Chris Childers)  Alcaeus, fragment 347.  https://www.literarymatters.org/12-1-alcaeus-347/

NASA Astronomy Picture of the Day  Sirius distance (8.6 light-years) and brightness  cited for astronomy facts only, not dog-days folklore.  https://apod.nasa.gov/apod/ap161215.html

National Dog Day (official site)  Confirms the August 26 date was chosen for a reason unrelated to Sirius or Roman astronomy.  https://www.nationaldogday.com/about1