Why hot weather is so hard on horses
UK summers are increasingly delivering heatwaves that catch owners and horses off guard, and with the Met Office recording more frequent and intense periods of extreme heat in recent years, horses (and the people who care for them) often don't have time to acclimatise.
Given time, horses can adapt to extremes of temperature, and some breeds are particularly efficient at it; the Arab horse, for example, evolved in desert conditions where a 30°C swing between day and night temperatures is normal. The problem is sudden heat, especially when a horse is also working hard.
Horses have a large muscle mass relative to their surface area, which is a disadvantage when it comes to shedding heat quickly. Heat is lost mainly through two routes:
- Radiation and evaporation of sweat - skin blood vessels dilate and bring blood to the surface so heat can escape, which is most visible in a sweating racehorse but happens in every horse, even small, hairy ponies.
- Respiration - the breathing rate rises to help lose heat, and this is especially noticeable in horses with compromised airways, such as those with inflammatory airway disease or equine asthma.
Cooling only works when there's a temperature “gradient” between the horse and the air around it. When the air temperature itself climbs towards 30°C, that gradient shrinks and the horse's natural cooling becomes far less effective.
Signs of heat stress and heatstroke in horses
Knowing the early warning signs lets you act before a hot horse becomes a veterinary emergency. Contact your vet promptly if you notice:
- Excessive sweating, or unusually, no sweating at all (anhidrosis)
- A heart rate that stays high and doesn't recover after rest
- Rapid, laboured breathing
- Lethargy, dullness or reluctance to move
- Loss of coordination or an unsteady gait
- A rectal temperature above roughly 39–40°C
- Reduced appetite or signs of colic
If you suspect heatstroke, move the horse into shade immediately, begin cooling with cold water and call your vet without delay.
Everyday ways to keep your horse cool
Water and forage
Water consumption rises in hot weather to replace fluid lost through sweat and respiration, so ad lib clean water is essential at all times. If horses are out at grass with self-filling troughs, check these regularly, as they can quickly turn green with algae in warm weather and become unappetising. Adding water to feed, or offering soaked or wet hay, can help boost overall fluid intake, since forage holds water in the hindgut and acts as a reservoir the horse can draw on.
Be aware that if a hot horse doesn't drink enough, or fluid is drawn excessively into the gut, impaction colic can result, so monitor droppings and water intake closely in a heatwave.
Shade and ventilation
Avoid exercising horses during the hottest part of the day and provide shade, either via field shelters, trees, or by bringing horses in during peak heat. If stabling, ventilation is critical: traditional stables, especially wooden ones, can heat up like saunas. Electric fans (positioned and used safely, away from cables and bedding) can make a real difference to airflow and comfort.
Electrolytes
Electrolytes are essential for normal muscle function and are lost in sweat. A tablespoon of plain kitchen salt added to feed will help replenish them, or you can use a commercially available equine electrolyte supplement. Electrolytes can be added to water, but always offer plain fresh water alongside, as some horses dislike the taste and will refuse to drink it otherwise.
Riding and competing in hot weather
Sometimes riding or competing in the heat of the day is unavoidable. To prepare:
- Bring plenty of water from home, even if water is available at the venue.
- Take your horse's own water bucket; many horses are reluctant to drink from an unfamiliar one.
- Park the lorry or trailer in shade where possible, with windows open and the ramp down for airflow.
- Run onboard fans periodically if your horsebox has them.
- Attend to your horse in the shade wherever you can and keep drinking water available whenever you're not actively riding.
- Allow access to forage, which helps hold water in the gut for the horse to draw on later.
How to cool a horse down after exercise
Research carried out ahead of the 1996 Atlanta Olympics - where heat and humidity were a major concern - transformed how riders and vets approach post-exercise cooling, and those lessons still apply today. At major events you'll often see cooling tents with misting fans, but most yards and local shows won't have this luxury. The single most effective method remains applying copious amounts of cold water over the horse's neck and body.
There's long been debate about whether you need to scrape excess water off afterwards, out of concern that the water heats up in the sun or “traps” heat. This isn't supported by the evidence: scraping isn't harmful, but the time it takes is better spent applying more water to the horse rather than removing it.
It’s not recommended to place cold, wet towels over a horse's neck or back. They rapidly become hot, insulating towels with no way for heat to evaporate away, which works against cooling rather than helping it. Offer water as soon as you finish riding or competing and encourage the horse to drink. If your horse sweats heavily and you compete regularly through summer, clipping can make it considerably easier to keep them cool, an option that's well-established for showjumpers and many competition horses clipped year-round.
Sun protection and flies
Keeping a horse cool is the priority in hot weather, but bright sunshine brings its own problems. Horses are just as prone to sunburn as people, and pink-skinned areas, particularly noses, should always be protected. A full-face fly mask that covers the nose is useful for horses turned out at grass and also helps keep flies away from the eyes; sun-block formulated for children (factor 50) is a good, horse-safe option and should be reapplied regularly.
Both biting flies, such as horseflies, and nuisance flies around the eyes are worse in summer, so an effective fly repellent is essential. Permethrin-based repellents applied across the horse tend to last longest and can also help against midges for horses prone to sweet itch.
Many owners also find lightweight, light-coloured fly rugs useful in summer; as well as repelling insects, pale colours reflect some of the sun's rays and can offer a small additional cooling benefit.
Frequently asked questions
Q: How do I know if my horse is too hot?
Look for excessive sweating (or unusually none at all), a heart rate that won't come down after rest, fast or laboured breathing, lethargy, and a rectal temperature above around 39-40°C. Any combination of these warrants an urgent call to your vet.
Q: Should I scrape water off my horse after hosing it down?
No, scraping isn't harmful, but it isn't necessary either. You're better off spending that time applying more cold water to your horse rather than removing it, since repeated, generous water application cools more effectively than a single hose-down followed by scraping.
Q: What should I feed a horse to help it cope with heat?
Offer ad lib clean water, soak hay or add water to feed to boost fluid intake and add a tablespoon of table salt or a commercial electrolyte supplement to replace minerals lost in sweat. Always provide plain water as well as electrolyte water, since some horses won't drink the latter.
Q: Is it safe to put a cold towel on a horse to cool it down?
No. A cold towel left on a horse heats up quickly and traps heat against the skin rather than letting it evaporate away, so it can do more harm than good. Pouring water directly onto the horse and letting it run off, repeated regularly, is far more effective.
Q: Can horses get heatstroke?
Yes. Heatstroke is a genuine veterinary emergency, particularly in horses working hard in high temperatures and humidity. Signs include a high body temperature, rapid breathing, weakness and collapse. If you suspect heatstroke, move the horse to shade, begin active cooling with water, and contact your vet immediately.
Q: What time of day is safest to ride a horse in summer?
Early morning or evening, when temperatures are lower, are generally safest. Avoid exercising horses during the hottest part of the day, typically late morning through mid-afternoon, especially during a heatwave.
Stay covered, whatever the weather
Hot weather can bring unexpected health risks, from heat stress to colic, so it's worth knowing your horse insurance covers vet's fees for these kinds of emergencies, as well as accidents and illness. To find out more, speak to a member of the KBIS team on 0345 230 2323 or email ask@kbis.co.uk