Here's a fact worth dining out on all week: the “dog days” of summer are literally named after a dog. Not as a joke about how your spaniel spends July flat on the cool kitchen tiles — though that fits — but after a real, specific, extremely bright dog in the night sky.
The short version: the dog days are named after Sirius, the Dog Star. In the ancient world, Sirius rose in the sky alongside the sun during the hottest part of summer, and people blamed the star for the heat. Two thousand years later, the dogs are still quietly taking the credit.
Meet Sirius, the Dog Star
Sirius is the brightest star in the entire night sky — so bright it can be mistaken for a planet. It sits in the constellation Canis Major, Latin for “the Greater Dog,” which is traditionally drawn as a dog following at the heels of the hunter Orion. Sirius marks the dog's nose or heart, depending on which old star map you follow. The name itself comes from the Greek Seirios, meaning “scorching” or “glowing” — fitting for a star this bright.
For most of the year Sirius is a winter star, blazing away on cold clear nights. But in high summer it does something the ancients found deeply suspicious.
Why a star got blamed for the heat
In midsummer, Sirius rises and sets at roughly the same time as the sun — it's up there in the daytime sky, hidden in the glare. Ancient Greek and Roman astronomers noticed that the year's most brutal heat arrived just as Sirius reappeared in the dawn sky after a spell of being invisible (its “heliacal rising”). They put two and two together and got five: they decided the brightest star must be adding its heat to the sun's, and that this double dose was what cooked the summer.
The Romans called this stretch dies caniculares — the “days of the dog star,” from canicula, “little dog.” That's where our English “dog days” comes straight from. Traditionally they run from around early July to mid-August — the very weeks we're in now.
They were, of course, completely wrong about the cause. Summer heat comes from the tilt of the Earth, not from a star 8.6 light years away (Sirius is far too distant to warm so much as a windowsill). But the name stuck, and it's rather lovely that the hottest, laziest weeks of the year are, etymologically, the dog's fault.
Two thousand years of the summer flop
The best part of the story is how little has changed. The Romans associated the dog days with lethargy, short tempers and general wilting — poets grumbled about them, and people did as little as possible until the cool of the evening. Sound familiar? Your own dog has independently rediscovered the exact same wisdom: sleep through the heat, conserve energy, and come alive when the sun finally drops and the pavement cools.
Which is really what the dog days are for. In the heat of mid-July the whole day funnels down to one good hour — the cool of the evening, when the walk finally belongs to the dog. We wrote a little love letter to exactly that this week: The Eight O'Clock Walk.
Looking after your own dog star in the heat
The ancients had the right instinct even if they had the wrong science. During the dog days, do as the dogs do:
- Walk in the cool. Early morning and the golden hour after the sun drops are kindest — both for temperature and for hot pavements. Our guide on protecting paws from hot pavements has the five-second back-of-the-hand test.
- Let them flop. A dog seeking out the coolest tile in the house isn't being dramatic — it's being sensible. Give them shade and a cool spot to retreat to.
- Keep water everywhere. Fresh water indoors and out, and a travel bottle or bowl for the evening walk.
- Save the games for the evening. When the lawn cools, that's the time for the zoomies and the rope toy — not the midday sun.
Frequently asked questions
Why are they called the “dog days” of summer?
They're named after Sirius, the Dog Star, the brightest star in the night sky and part of the constellation Canis Major (“the Greater Dog”). In the ancient world Sirius rose alongside the sun during the hottest weeks of summer, so the Romans called the period dies caniculares — the dog days.
When are the dog days of summer?
Traditionally they run from around early July to mid-August in the Northern Hemisphere — the hottest stretch of the year — though the exact dates have shifted slowly over the centuries as the stars' positions change.
Does Sirius actually make summer hotter?
No. Summer heat is caused by the tilt of the Earth toward the sun, not by any star. Sirius is about 8.6 light years away and has no effect on our weather. The ancients simply noticed the timing and drew the wrong conclusion — but the name stuck.
Happy dog days from Duke & Milo. Mind the hot pavements, chase the golden hour, and give your own dog star an extra fuss this week.