Preventing Heat Stress in Horses

Summer is a beautiful time to enjoy the outdoors with your horse. But as temperatures climb, so does the risk of heat-related illness. Just like humans, horses can suffer from heat stress and, in severe cases, heat stroke. That’s why it’s critical to understand how to recognize the signs and take proactive steps to keep your horse safe and comfortable.

What Is Heat Stress?
Heat stress occurs when a horse’s internal cooling system is no longer able to regulate body temperature effectively. This often happens during high temperatures, high humidity, or intense exercise. If left unmanaged, heat stress can lead to serious complications like dehydration, shock, or even collapse.
The horse’s normal body temperature typically ranges from 37.5–38.5°C (99–101.5°F). Anything above 40.5°C (105°F) is cause for concern and may indicate the onset of heat stroke—a potentially life-threatening emergency.

Warning Signs to Watch For
Knowing the signs of heat stress and heat stroke can make all the difference. Monitor your horse closely during warm weather or periods of exertion.

Common signs of heat stress include:

• Elevated rectal temperature (above 103°F / 39.5°C)
• Rapid breathing and flared nostrils
• Increased heart rate
• Lethargy or reluctance to move
• Excessive sweating or, conversely, no sweating
• Dehydration: tacky gums, sunken eyes, or reduced urination
• Diminished appetite

In severe cases (heat stroke), symptoms may escalate to:

• Rectal temperature exceeding 105°F (40.5°C)
• Staggering, incoordination, or collapse
• Very rapid heart and respiratory rates
• Extended skin tent when testing hydration
• Signs of agitation or distress

If you observe any of these signs, stop all activity, move your horse to a shaded area, and begin cooling them down immediately. If symptoms persist or worsen within 20 minutes, call your veterinarian.

Why Horses Struggle in the Heat
Despite being incredible athletes, horses are not as heat-tolerant as we might think. They generate a lot of heat during exercise due to their large muscle mass and relatively small surface area for heat loss. Sweating is their main cooling mechanism—losing up to 4 gallons per hour in extreme heat.
Unfortunately, high humidity prevents sweat from evaporating effectively, trapping heat and raising the risk of dehydration and electrolyte loss.

Contributing Risk Factors
Some horses are more vulnerable to heat stress than others. Keep an eye on:

• Foals and senior horses – less efficient thermoregulation
• Overweight or unfit horses – fat insulates, making it harder to cool down
• Long travel – confined spaces with poor airflow and limited water access
• Thick coats or heavy blanketing

Prevention Strategies
When it comes to heat stress, prevention is always the best medicine. Try these management strategies to help your horse beat the heat:

Modify Exercise Routines

• Avoid riding during peak heat (typically 12–5 PM)
• Use early mornings or cooler evenings for training
• Watch for early fatigue—even low-intensity work in heat can be harmful

Prioritize Hydration & Electrolytes

• Always provide access to clean, cool water
• In hot weather, horses may drink up to 19 gallons per day
• Use electrolyte supplements to replenish minerals lost through sweat (especially sodium, potassium, and chloride)
• Avoid giving large quantities of plain water alone after heavy sweating, as this can dilute existing electrolytes

Utilize Cooling Tools

• Install fans or mist systems in barns and shelters
• Walk your horse in shaded areas after workouts
• Hose down with cool water
• Use ice packs or cold towels on the neck and chest if temperatures remain high
• Skip cooling sheets during active heat stress—they can trap heat if the horse is still sweating

Consider Clipping

• Thick coats can trap heat—body clipping in the summer can help some horses cool more efficiently

Emergency Response: Cooling Down a Hot Horse
If your horse becomes overheated:

1. Move to shade or a well-ventilated area
2. Hose down with cool water continuously (focus on large muscle groups and neck)
3. Walk gently to promote circulation
4. Use ice on large blood vessels along the neck and shoulders if the temperature is dangerously high
5. Offer small sips of water with electrolytes
6. Monitor rectal temperature—if it doesn’t drop below 103°F (39.5°C) within 15–20 minutes, call your vet

Conclusion

Heat stress is a real concern during the summer months, but it’s also highly preventable. Understanding the warning signs and taking simple, proactive steps can protect your horse’s health and ensure you both enjoy the season safely.