Horse Temperature: Normal Range, Fever and Warning Signs

Horse temperature is the easiest health reading to take and the one most often overlooked. A healthy adult horse at rest sits between 37.5 and 38.2 degrees Celsius, and it only takes 0.5 degrees above 38.5 to move into the fever range that warrants a call to the vet. Yet most owners have no idea what their own horse's baseline is, the figure it shows on an ordinary morning when everything is fine. This guide gives you the exact ranges for adults and foals, a safe step-by-step method for taking the reading, how to interpret every band from 36 to 40 degrees, and above all the vital distinction between an infectious fever and heat stress, two emergencies that call for exactly opposite responses.

Horse temperature: the normal figure to know by heart

A healthy adult horse at rest shows a rectal temperature between 37.5 and 38.2 degrees Celsius. The reference figure most equine vets work to is around 38 degrees. That range is narrow: contrary to what many people assume, a horse is not an animal whose temperature drifts freely. Half a degree above the upper limit already carries clinical meaning.

The fever threshold starts at 38.5 degrees in an adult measured calmly, with no prior exertion and no exposure to strong heat. That figure is not a turn of phrase: it is the point at which an owner should stop observing and start acting, by monitoring closely and then calling the vet if the reading is confirmed.

One clarification that prevents a lot of mistakes: only a rectal reading tells you about core temperature. Feeling the ears, the base of the neck or the legs tells you about peripheral circulation, not core body heat. A horse can have ice-cold ears and a 39.2 degree fever, or ears warmed by the sun and a perfectly normal temperature. There is no reliable shortcut.

The single most useful habit is the one almost nobody adopts: take your horse's temperature three or four times over the course of a month, while everything is fine, always at the same time of day. That gives you its personal baseline. Some horses naturally run at 37.6 degrees, others at 38.1. The day yours reads 38.4, you will know whether that is an unremarkable figure or a 0.8 degree jump above its usual.

Vital signs chart for a horse at rest

An adult horse at rest combines three reference values: a rectal temperature of 37.5 to 38.2 degrees, 28 to 44 heartbeats per minute and 8 to 16 breaths per minute. Temperature is never read on its own. Equine vets talk about TPR for Temperature, Pulse, Respiration: that trio is the foundation of any remote assessment, and it is exactly what your vet will ask for on the phone before deciding whether to come out. Taking all three takes five minutes and turns a vague call into a useful one.

The pulse is taken under the jaw, on the facial artery, or behind the elbow with a stethoscope. The respiratory rate is counted by watching the flank move for 30 seconds and doubling the figure, on a horse that has not been disturbed. Capillary refill time is checked by pressing the upper gum with your thumb: the blanched patch should regain its colour in under two seconds.

A reading of 38.4 degrees in a horse with a pulse of 32 and a respiratory rate of 12 tells a very different story from the same reading with a pulse of 68 and a rate of 30. In the second case, temperature is not the worrying figure.

How to take a horse's temperature step by step

Temperature is taken rectally, with a lubricated digital thermometer inserted about 5 centimetres, standing to the side of the horse at all times and never directly behind the hind legs. There is nothing technically difficult about it once the routine is in place: the only real risk is a safety risk, not a measurement one. A flexible digital thermometer with a rounded tip belongs in every yard first aid kit, alongside a pair of scissors or a head torch, the kind of kit you will find in our riding accessories.

The full routine, worth pinning up in the tack room:

• Get everything ready before you walk into the stable: digital thermometer, lubricant (petroleum jelly or a neutral gel), paper towel, disinfectant and a notebook to record the reading.
• Ask a second person for help if your horse is not used to it: they hold the headcollar and keep the horse occupied while you work.
• Never stand directly behind the hindquarters. Approach the hind end from the shoulder, one hand resting on the croup, so the horse always knows where you are.
• Apply plenty of lubricant to the tip, move the tail to one side with a firm but gentle hand, then insert the probe about 5 centimetres.
• Angle the probe towards the rectal wall rather than letting it float in the middle: a probe resting against a dropping gives a falsely low reading.
• Hold the thermometer in place until it beeps, usually 30 to 60 seconds depending on the model.
• Write down the reading, the time and the context (at rest, after work, hot day).
• Dry and disinfect the probe before putting it back in the kit.

Two rules close the routine. First: wait 30 to 60 minutes after exercise before taking a reading, otherwise you are measuring the heat of work rather than the state of health. Second: never take a temperature straight after travelling or after any stressful handling, for the same reason.

Reading the result: what 36, 38, 39 or 40 degrees means

Below 37 degrees the horse is hypothermic, between 37.5 and 38.2 degrees everything is normal, from 38.5 degrees there is a fever, and above 39.5 degrees the situation becomes a veterinary emergency. A raw figure means nothing until you place it on a scale. Here is the reading band by band, in an adult horse measured at rest, well away from any exercise.

• Below 37 degrees: hypothermia. Abnormal in any context and to be treated as a serious warning sign. Call your vet, especially if the horse is dull, if the extremities are cold or if there is any suggestion of colic or shock.
• 37 to 37.4 degrees: on the low side. Acceptable in some horses very early in the morning or in hard frost, but worth rechecking an hour later and cross-referencing with pulse and appetite.
• 37.5 to 38.2 degrees: normal range. Nothing to report as long as the horse is eating, drinking, passing droppings and behaving normally.
• 38.3 to 38.4 degrees: borderline. Common in late afternoon, in warm weather, or in a horse that has just been moved. Recheck in one to two hours under calm conditions.
• 38.5 to 39 degrees: confirmed fever. Close monitoring, a reading every two to three hours, and attention to appetite, gut movement and attitude. Call your vet, particularly if other horses on the yard are showing similar signs.
• 39 to 39.5 degrees: marked fever. Call the vet rather than waiting until tomorrow. Have the full TPR and the last 48 hours of history ready.
• Above 39.5 degrees: emergency. Call the vet immediately. If the context is hard work, travel or extreme heat, think heat stress first and start the cooling described below while you wait.

Never give medication on your own initiative, not even something left in the yard cupboard from a previous prescription. An anti-inflammatory brings the fever down without treating the cause, masks how the case is developing and deprives your vet of the information needed to reach a diagnosis.

The normal variations that should not worry you

A healthy horse's temperature naturally varies by 0.5 to 1 degree over the course of the day, driven by circadian rhythm, work, ambient heat, travel, stress and digestion. A great many false alarms come from not knowing about these physiological swings. A healthy horse's temperature moves through the day, and that variation is well documented.

• Circadian rhythm: temperature is lowest in the early morning and highest in late afternoon, with a typical swing of 0.5 to 1 degree over 24 hours. A horse at 37.7 degrees at 7am may read 38.4 degrees at 6pm with nothing wrong at all.
• Work: sustained exercise pushes temperature up by several degrees. That is normal, and the return below 38.5 degrees should happen within 30 to 60 minutes of finishing.
• Ambient heat: a 32 degree day and a poorly ventilated stable shift every reading upwards.
• Travel: a combination of heat, stress and static effort. Wait until the horse has been settled and quiet for an hour before measuring.
• Stress: the vet, the farrier, separation from a field companion, a thunderstorm. Adrenaline raises temperature briefly.
• Digestion: fermentation in the hindgut produces heat, and a reading taken straight after a generous haynet can come out slightly higher.
• A mare in season: a slight rise is possible during oestrus.
• An unsuitable rug: a horse rugged too warmly for the season easily gains several tenths of a degree.

The rule that cancels out all these variables is simple: always measure under the same conditions, ideally in the morning, when the horse is quiet, before work and before feeding.

Fever in horses: common causes and associated signs

The most common causes of fever in horses are viral infections (equine influenza, equine herpesvirus), bacterial infections (strangles, abscesses, infected wounds), piroplasmosis, post-vaccination reactions and certain digestive complications. Fever is not a disease, it is a response by the body. It tells you the immune system is fighting something, and it is that something you need to identify. The most common causes in horses are as follows.

• Viral infections: equine influenza and equine herpesvirus top the list, often with a sudden temperature spike and rapid spread through the yard.
• Bacterial infections: strangles, abscesses, infected wounds, dental or foot infections. A brewing foot abscess regularly produces a moderate fever before any obvious lameness appears.
• Parasitic disease: piroplasmosis, transmitted by ticks, sometimes with a high fever and yellowish mucous membranes.
• Post-vaccination reaction: a moderate rise in the 24 to 48 hours after vaccination, usually mild and short-lived.
• Digestive complications: some colics and enteritis cases come with a fever, which strongly steers the diagnosis.

The signs that accompany a fever deserve to be recorded as carefully as the reading itself:

• dullness, with the horse hanging back at the rear of the stable or the field;
• refusing food, wholly or partly, including feeds it normally enjoys;
• abnormal sweating at rest, or on the contrary a dry, dull coat;
• congested mucous membranes, redder than usual;
• slowed gut transit, with fewer, drier or absent droppings;
• faster breathing and flared nostrils at rest;
• a low-carried neck, ears barely moving, reduced responsiveness.

A feverish horse that keeps eating normally and a feverish horse that refuses everything are not equally urgent. The second warrants an immediate call. For the foot problems that often come with a rise in temperature, our article on laminitis in horses sets out the signs to cross-reference with the temperature reading.

Heat stress or fever: two emergencies not to be confused

An infectious fever comes on at rest and is managed quietly while you wait for the vet, whereas heat stress comes on after exercise or travel and calls for immediate active cooling with cold water. This is the most important distinction in this article, and the one most guides treat separately even though it has to be settled in a single moment, thermometer in hand.

The horse is at a thermal disadvantage. Its muscle mass is enormous relative to the body surface available for heat exchange, and a large share of the energy produced by muscular work is released as heat rather than movement. Its main route of heat loss is sweating, followed by evaporation from the coat surface: work in equine physiology relayed by the Institut Français du Cheval et de l'Équitation estimates that sweat evaporation accounts for around 70% of heat dissipation during sustained exercise. It is also why the Fédération Française d'Équitation regulates competition during summer heatwaves.

One biological detail explains why that sweating works despite a naturally water-repellent coat: horse sweat contains a surfactant protein called latherin, found almost exclusively in equids. It lowers the surface tension of sweat and lets it travel through the hair to spread across the coat surface, where it can finally evaporate. That protein is what produces the characteristic white foam on the neck and between the hind legs after work. Without it, sweat would stay trapped at the base of the hair and cooling would be far less effective.

Here is how to tell the two clinical pictures apart:

Faced with heat stress, action comes first: move the horse into the shade and into moving air, and apply cold water continuously over the whole body, concentrating on the neck, the legs and the inside of the thighs, scraping off the warmed water before applying more. Offer water to drink freely and call the vet.

Faced with an infectious fever, a reflex cold hosing is not the answer. The horse should be kept quiet, out of draughts, with fresh water available, while the vet is contacted. Keeping the horse away from the others is a sensible precaution until the cause is known.

Hypothermia: the silent danger in a chilled horse

An adult horse is hypothermic as soon as its rectal temperature drops below 37 degrees, a situation that often signals a more serious emergency than a fever. It attracts far less attention than a fever, yet it frequently points to a graver problem. The most common contexts are the newborn foal that has not suckled quickly enough, the old, thin horse exposed to wind and rain, the clipped horse under-rugged in winter, and the horse in shock from severe colic or blood loss.

The signs to look for:

• cold extremities, with ears and lower legs freezing to the touch;
• shivering, then shivering that stops, which signals deterioration rather than improvement;
• profound dullness, with the horse no longer responding to you;
• pale mucous membranes and a lengthened refill time.

What to do: dry the horse if it is wet, get it out of the wind, rug it, offer hay so fermentation generates heat, and call the vet without delay. What to avoid: warming it abruptly with a direct heat source, walking a horse that is in shock, or waiting until tomorrow in the hope of spontaneous improvement. A set of rugs and protection suited to the season, like the riding equipment you keep in the tack room, remains the best prevention for clipped or elderly horses.

Special cases: foal, pregnant mare, elderly horse and sport horse

A newborn foal can reach 39 degrees with nothing wrong, a pregnant mare's temperature drops slightly before foaling, an elderly horse sometimes mounts only a blunted fever, and a sport horse can climb to 41 degrees after hard work. Reference values are therefore not universal: four profiles need an adjusted reading.

• The newborn and young foal: its normal range is higher, with readings that can reach 39 degrees in the first days of life with nothing wrong. Its reserves, however, are very slim: an infection develops over hours, not days. In a foal, any abnormal temperature, high or low, warrants a call to the vet the same day.
• The pregnant mare: in late gestation, a slight drop in temperature in the 24 to 48 hours before foaling is an indicator used on studs, alongside relaxation of the pelvic ligaments and waxing up. That indicator is only worth anything if you have been taking daily readings in the preceding weeks.
• The elderly horse: its febrile response can be blunted. A genuinely infected veteran sometimes shows no more than 38.4 degrees, a figure that would have been reassuring in a young adult. In an older horse, dullness and loss of appetite matter more than the number.
• The sport horse: after hard work, temperature can climb to 40 or even 41 degrees. What matters is not the peak but the speed of return to normal: below 38.5 degrees within 30 to 60 minutes of finishing. A slower return points to poor recovery, a fitness problem or weather conditions unsuited to the session. Coherent feeding has a direct effect on that recovery capacity, as set out in our guide to feeding your horse.

In every case, keeping a record book for each horse, stored in the tack room with the everyday horse accessories, completely changes the quality of the conversation with your vet. A single reading is a piece of information; a series of readings is a diagnosis in the making. Plenty of owners pin their vital signs sheet up by the stable, next to the horse decor and the name plate, so it is to hand without hunting for it.

Frequently asked questions about horse temperature

The seven questions below are the ones owners ask most often about their horse's temperature, each with a direct answer.

How can you tell if a horse has a fever?

The only reliable method is a rectal reading with a digital thermometer. Above 38.5 degrees in an adult at rest, there is a fever. The associated signs that strengthen the suspicion are dullness, refusing food, faster breathing and congested mucous membranes. Feeling the ears tells you nothing.

At what temperature does a horse have a fever?

Fever starts at 38.5 degrees in an adult horse measured at rest, well away from any exercise. Between 38.5 and 39 degrees, close monitoring is required. Above 39.5 degrees, it is an emergency that warrants an immediate call to the vet.

What is a horse's normal baseline temperature?

An adult horse at rest sits between 37.5 and 38.2 degrees, with a reference figure around 38 degrees. Each horse nonetheless has its own normal within that range, which is why it is worth taking several readings while everything is fine.

What is the normal rectal temperature?

Normal rectal temperature matches the horse's reference range exactly, meaning 37.5 to 38.2 degrees in an adult and up to 39 degrees in a foal a few days old. It is the only reading that reflects genuine core temperature.

What should you do for a horse with a fever?

Take the full TPR (temperature, pulse, respiration), note appetite, gut movement and behaviour, keep the horse away from the others if contagion is possible, leave fresh water available and call your vet. Do not give any medication on your own initiative.

How do you bring a horse's fever down?

Bringing a fever down is the vet's job, and they will decide on the treatment that fits the cause. Your part is to keep the horse quiet, out of draughts, with water freely available, and to track the temperature every two to three hours. Reflex cold hosing applies only to heat stress, not to an infectious fever.

What should you give a horse with a fever?

Fresh water, freely available, is the absolute priority, because fever dehydrates. Offer good quality hay and palatable feed to keep the gut moving, without forcing anything. No medication, no supplement and no dosage should be decided without your vet's advice.