The hour before an emergency

The thing about heat is that it almost never kills an animal suddenly. By the time a dog is being rushed to a clinic in the back of a car, or a horse is on the ground in a stable yard, the body has been failing for some time — usually thirty minutes, often an hour, occasionally longer. The owner's experience of that hour is what determines whether the animal lives.

This is worth saying plainly, because the public framing of heat-related deaths is built around the dramatic ones — dogs locked in cars, horses collapsing on a hot transport day. Those exist, and they are awful, but they are not the main story. The main story is the much more ordinary one: a long walk on a warm-but-not-extreme afternoon, a hack that went on twenty minutes too long, a Frenchie playing in the garden until they stopped being able to cool themselves down. The animal didn't die because of cruelty or carelessness in any obvious sense. They died because their body crossed a threshold and the person with them didn't know it was happening.

Most of that is preventable, but only if you know what the hour before an emergency actually looks like.

What the body is doing under heat

Dogs do not sweat in any meaningful way. They have a very small number of sweat glands in their paw pads and almost nothing else. The way a dog manages temperature is by panting — moving air across the wet surfaces inside the mouth and upper airway so that water evaporates and takes heat with it. It is a relatively inefficient system at the best of times. In a dog with a normal muzzle it works. In a brachycephalic dog — French Bulldog, Pug, English Bulldog, some Boxers, some shih-tzu types — the airway is the wrong shape for the cooling job, and the system is already half-broken before any heat arrives. That is not a moral failing on anyone's part; it is anatomy.

Horses do sweat, and well. They can lose ten or twelve litres of fluid an hour on a hot day. The problem is that sweat only cools them if the air is dry enough to evaporate it and slow enough to take the heat away. In a hot, still, humid yard, a sweating horse is producing very little cooling effect and is rapidly losing the water and electrolytes that keep them functioning. The horse looks like they are coping — wet coat, breathing through the nostrils — long after they have stopped genuinely cooling.

In both species, when the body's cooling system can no longer keep up with the heat being generated or absorbed, the core temperature starts to rise. A normal dog runs at 38–39°C; a horse at 37.2–38.5°C. Above 39.5°C in a dog and 39°C in a horse, the body is in trouble. Above 41°C, in either species, proteins in the body begin to denature — the kidneys, the gut, the brain, the muscles all start to be damaged in a way that doesn't always come back, even if you cool the animal down afterwards.

There is no obvious external moment at which this happens. The animal does not collapse the second they cross 40°C. They just keep going, slightly worse, slightly worse — and then they are in an emergency, and you wonder when it actually changed.

What the hour before looks like

In a dog, the signs of heat moving from "warm and working hard" into "in trouble" are specific and consistent, and almost none of them are dramatic on their own. The dog's panting becomes faster and more shallow, and importantly, doesn't slow down when they stop and rest. The tongue gets bigger, more bright red, sometimes dark red. The saliva becomes thick and ropy rather than the usual loose drool. The dog looks slightly lethargic but also agitated — pacing, then lying down, then up again. They will often refuse water at this stage even though they obviously need it. Their ears feel dry and hot inside. They may stumble slightly, or stand strangely, or look away from you when you try to engage them.

None of those signs, alone, mean an emergency. Taken together, in the same animal, in the same fifteen minutes, they mean you have about half an hour before something serious happens.

In a horse, the same kind of sequence is rougher and less visible. The nostrils flare wider; the breathing becomes quick and shallow rather than deep, often more than 60 breaths a minute (a horse at rest is around 8–16). The sweat changes character — it can become thick and white, the so-called lather, which looks like the horse is sweating heavily but is actually a sign the sweating system has lost efficiency. The horse may stand with their head low, refuse to move forward, or become trembly in the hindquarters. Eyes can look glazed or unfocused. One of the most useful, and most overlooked, signs is the disappearance of gut sounds — a healthy horse's belly is noisy almost all the time; a horse heading into trouble goes quiet. If you can listen with a stethoscope, do; if you can't, learn to listen with your ear pressed to the flank.

In both species, the animal at this stage is recoverable. You have a window of perhaps thirty to sixty minutes during which the right actions almost always work, and the wrong actions — including doing nothing — make the next stage inevitable.

What the emergency itself looks like

If you've missed the window, the signs change. In dogs: vomiting, often with blood. Diarrhoea, often with blood. Confusion or stumbling so pronounced that they can't stand. Gum colour changing from healthy pink to pale, grey, or purple. Seizure. Loss of consciousness. In horses: collapse. Inability to stand. Severe trembling. Eyes rolled or dull. Total absence of gut sounds. Marked depression and unresponsiveness.

At this stage you are in a true emergency, and you have minutes rather than half an hour. Call the vet on the way, not when you get there. Cool aggressively. Do not wait.

What to do in the window

The single most useful intervention in the window before an emergency is also the most misunderstood: cooling.

There is a stubbornly popular belief that you should pour ice water over an overheating animal. This is wrong, in dogs and worse in horses. Ice-cold water constricts the blood vessels at the skin, which traps heat in the core. It also causes vasoconstriction-driven shock in some horses. What you want is cool water — tepid, hose-pipe temperature in summer, not chilled — applied generously to the parts of the body where heat exchanges most efficiently: the neck, the chest, the inner thighs, the belly, the paw pads in dogs, and the legs in horses. Keep applying it; the warm water can be removed and replaced with more cool. Add air movement: shade, a fan, walking the horse gently if they will, opening windows or doors. Offer small sips of room-temperature water, not great gulps, and only if the animal is conscious and able to swallow.

Call the vet in the window, not at the emergency. A good vet will talk you through cooling on the phone, and will be ready when you arrive if it's needed. The early call is what often makes the difference between a vet visit and a vet visit with a body in it.

What kills, in the ordinary cases

Closed cars, including on what feels like a cool day. A car's interior climbs to dangerous temperatures within fifteen minutes on a 22°C day — the kind of mild summer afternoon at which no British owner thinks twice about leaving a dog in the car for a few minutes. By the time the owner returns, the dog may be past the recoverable window.

Pavement and tarmac. The radiant heat from a sunny pavement at midday is far higher than the air temperature implies. A dog walked at midday is being heated from below as well as above, and the paw burns themselves are an additional welfare disaster that owners often don't see until the dog limps the next day.

Exercise after eating, in horses. Hot days plus full hay nets plus competition or transport is the classic colic and heat-stress combination.

Brachycephalic dogs at any time on a warm day. Their cooling system is half-functional. The threshold at which a Frenchie or Pug starts to struggle is around 20°C of ambient temperature; for a Labrador, it's 25°C or higher. If you have a brachycephalic breed, summer requires recalibration of what a "normal" walk looks like.

Sealed transport — horse boxes parked in the sun, dogs in vans, both with the windows up "just for a minute." Nothing in animal welfare is more brutally efficient at killing than a sealed metal box in direct sun.

The biggest single myth

The biggest one — the one that genuinely kills the most animals every summer — is the idea that the dog or the horse will "let you know" when they're struggling. They don't. They keep working until they can't, because the instinct to please, to keep going, to not look weak, is deeper than the instinct to flag exhaustion. By the time most owners report noticing something was wrong, the body had already crossed two or three internal thresholds. The animal can't tell you. You have to read them.

That reading is a learnable skill. None of the signs in this piece are exotic. They are visible to anyone paying attention, in the animal in front of them, in good light. The work of summer ownership is to pay that attention before, not during, the emergency.

The kind summary

If you take one thing from this, take this: on warm days, with your dog or your horse, slow down by about a third. Walk earlier. Hack earlier. Build in shade. Carry water — for both of you. Watch for the panting that doesn't slow with rest, the breathing that gets shallower, the silence in a horse's belly, the small change in how an animal stands. None of these are dramatic on their own. Taken together, in the same fifteen minutes, they mean the window is open and you have perhaps half an hour to use it.

The vets we work with talk about this every June. The same conversation, every year, with owners who didn't know what they were looking at. Almost every one of those animals could have been kept on the right side of the line. The owner is the only person on the scene when it matters. That is the whole of it.

— Rene