Canadians are practised at the cold. A February walk gets planned — the coat, the boots, the salt, the time. Then July arrives, the same walk happens at the same hour out of habit, and the risk has quietly inverted.
Heat is the more dangerous of the two seasons for a dog, because cold gives you warning and heat does not. A dog struggling in the cold slows down, lifts a paw, turns for home. A dog overheating often keeps going, because it is with you and that is what it does.
The same rule as winter, pointed the other way
There is no single temperature at which walking a dog becomes unsafe, and the reason is the same one that makes winter charts useless: tolerance varies enormously between animals. The American Veterinary Medical Association declines to give a threshold and points instead at coat, body fat, activity level and health.
The dogs at elevated risk are worth naming, because owners routinely misjudge them:
- Flat-faced breeds. A shortened airway is a less effective cooling system, and panting is how a dog sheds heat. This is the single largest risk factor and it is structural.
- Overweight dogs, for whom warm-weather exertion is harder on every system at once.
- Very young, elderly, and unwell dogs, and any dog with heart or respiratory disease.
- Thick double coats, which insulate against heat as well as cold. Shaving one is not a reliable way to prevent heatstroke and is not a decision to take on a hot afternoon: AVMA’s guidance is to ask your veterinarian whether your dog would benefit from a warm-weather haircut or other protection. There are medical and grooming reasons to clip a coat; “it is hot” on its own is not one we would act on without that conversation.
- Dogs that will not self-regulate. The retriever that would fetch until it collapsed is not going to tell you when to stop. You have to.
Add humidity to the reading. A humid 26 °C is harder work than a dry 30 °C, because evaporative cooling is what panting relies on and humid air gives it less to work with.
Parked cars: the one with no judgement call in it
The AVMA is unambiguous: never leave a pet in a car, even in the shade or with the windows cracked, because cracking the windows makes no difference. What it publishes is a table of how far the inside of a vehicle rises above the outside temperature: about 19 °F (roughly 11 °C) in ten minutes, 29 °F (16 °C) in twenty, 34 °F (19 °C) in thirty, and 43 °F (24 °C) at an hour.
The figure worth remembering is not any single number but AVMA’s note beside the table: that rise is much the same whether it is 70 °F or 110 °F outside. So a pleasant 22 °C afternoon puts the inside of the car past 33 °C in half an hour, which is why “it is not even that hot today” is not the reassurance it sounds like. These are averages across vehicles, not a promise about yours.
There is no version of this where a quick errand is fine. Plan the outing so the dog can come with you or stay home — those are the two options.
The pavement test, and why the back of your hand
Asphalt absorbs heat all day and holds it well past sunset. Dogs and cats can sustain third-degree burns to the pads from hot asphalt or sand, and a dog will keep walking on it because you are walking on it.
Put a hand flat on the surface before you commit to a route. If you cannot hold it there comfortably, neither can your dog, and the answer is grass, shade or a different time of day.
We have stopped giving the seven-second version of this test as a threshold. Veterinary sources that publish a duration do not agree on one — VCA’s is that if you cannot hold your palm on the pavement for over ten seconds it is too hot for a young dog to walk on — and that disagreement is the useful information: it is a rough screening test, not a measurement, and no count turns a surface safe. Do it on the actual route rather than your driveway, because dark asphalt, a metal grate and a shaded boulevard are three different surfaces. Burned pads may look swollen, red or blistered, and they need veterinary attention rather than a home dressing.
The practical fix is timing, not gear. Walk early and late, use grass and shade, and shorten the midday outing to what the dog needs rather than what it is used to.
Heatstroke: what it looks like
Knowing where you would go, before the afternoon you need it, is the whole argument of the emergency preparation guide — and summer is exactly when people are furthest from their own clinic.
Wildfire smoke, which is now a Canadian summer problem
This is the part that has changed in the last few years and that almost no pet-care advice has caught up with.
Canada publishes the Air Quality Health Index, a scale from 1 to 10+ where 1–3 is low risk, 4–6 moderate, and 7 or above high. During smoke events, Special Air Quality Statements are typically issued when the AQHI is expected to reach 7 or more, and Air Quality Advisories when it reaches 10 or more for a sustained period. Quebec publishes InfoSmog on the same principle.
Those numbers are set for people, and no equivalent index exists for dogs. But they are a usable proxy, and the sensible reading is conservative: treat a high-AQHI day the way you would treat a heat warning. Keep the dog indoors as much as you can, cut exertion rather than duration alone — a sniffing walk asks far less of the lungs than a run — make sure water is always available, and pay attention to any animal that already has a heart or airway condition, or a flat face.
The household measures that protect you protect the dog: windows and doors closed, and a portable air cleaner with a HEPA filter in the room where everyone actually spends time. If smoke where you live comes with evacuation warnings rather than just poor air, the preparedness guide covers the part that has to be arranged in advance.
If your dog is coughing, retching, breathing with visible effort, or unusually lethargic on a smoke day, phone your clinic. Breathing difficulty is on every veterinary list of things that warrant immediate attention, and smoke is not a reason to discount it.
Water, and the thing to check first
Swimming is excellent exercise and cools a dog properly. Two cautions worth carrying.
Not every dog can swim, and confidence is not competence — deep-chested and heavily muscled dogs in particular can be poor swimmers. A properly fitted flotation vest is not silly on a boat or in moving water.
And check local advisories before letting a dog into standing or slow-moving fresh water in warm weather. Municipalities and provincial health authorities post closures and water-quality warnings for specific lakes and beaches, and those notices exist precisely because the risk is real and local. A dog that swims will also drink, which is why "we were only there ten minutes" is not the reassurance it sounds like.
A summer kit and a summer habit
- Collapsible bowl and more water than you think, on every outing
- The back-of-hand pavement test, on the route you actually walk
- Walks moved to early morning and late evening, not shortened at noon
- Shade available wherever the dog is left, including the yard
- A flotation vest for a boat, moving water, or a dog that is a weak swimmer
- Local beach and lake advisories checked before swimming
- The AQHI checked on smoke days, and exertion cut rather than just duration
- Your nearest emergency hospital's address saved before you travel anywhere
- A plan for every outing that answers: where does the dog wait if I go inside?
Travel, cottages and the long drive
Summer is when Canadians go furthest from their own veterinary practice, which changes the calculation rather than removing it. Never leave an animal in a parked vehicle at a rest stop, look up a clinic and an emergency hospital near the destination before leaving, and remember that a car's air conditioning is equipment rather than comfort. The travel guide covers restraint, lodging and the veterinary side of the destination.
If the trip is to a cottage or a trail, the parasite question changes too — blacklegged ticks are established across a good deal of southern and eastern Canada, and a dog that spends August in long grass is a different risk profile from one that walks a city block. Parasite prevention by region and season covers what actually drives the timing.
The short version
Read the dog, not the thermometer — the same rule as winter, pointed the other way. Flat-faced, overweight, elderly and unwell dogs need a more cautious plan than the one that works for the dog next door.
Never leave a dog in a parked car, for any length of time, in any amount of shade. Test the pavement with the back of your hand before you commit to a route. Move walks to the ends of the day rather than shortening them in the middle. Check the AQHI when there is smoke, and cut the effort rather than only the distance.
And know where the emergency hospital is before July, because the whole point of heat is that it does not give you the warning the cold does.
