Horse Care in Hot Weather: Preventing Heat Stress and Dehydration

Horses generate heat from normal digestion and from exercise. In warm weather, they rely heavily on sweating to lose that heat. If the air is hot, humid, still, or all three, sweat evaporation becomes less effective. That means the horse may keep producing sweat without cooling well.

Dehydration makes the problem worse. Merck notes that dehydration before exercise leads to higher core temperatures during exercise. Horses also lose important electrolytes in sweat, especially sodium and chloride, so replacing water alone may not always be enough for hard-working or heavily sweating horses.

Early signs can be easy to miss. Watch for heavy sweating, very little sweating despite heat, hot skin, fast breathing, a heart rate that stays elevated after rest, dullness, weakness, stumbling, tacky gums, or sunken eyes. Some horses become irritable or restless before they look obviously sick.

More serious signs include persistent body temperature above about 102°F after exercise, worsening weakness, neurologic changes, collapse, or inability to recover normally. Heat stroke is an emergency. PetMD notes that body temperature above 105 to 106°F can become life-threatening in horses.

Provide unlimited access to clean water at all times. Many horses prefer ambient to cool water rather than very cold water, and some drink better when multiple buckets or troughs are available. Shade is essential in turnout areas, and barns should have good airflow. Fans can help in appropriate, safe setups.

Plan exercise for early morning or later evening. Build in walk breaks, shorten intense sessions during heat waves, and allow gradual acclimation when a horse is new to hot weather or returning to work. ASPCA guidance for horses also emphasizes fresh water, minerals, and adequate shade on hot, humid days.

If your horse is hot after exercise, active cooling matters. Merck advises hosing the horse with cool water and removing the water intermittently with a sweat scraper so heat is not trapped against the skin. Repeating that cycle, combined with rest and airflow, can help the horse cool more efficiently.

Do not wait too long if recovery seems slow. A horse that remains very hot, keeps breathing hard, has a high heart rate that does not come down, or seems mentally dull needs prompt veterinary attention. See your vet immediately if there is collapse, severe weakness, or neurologic change.

Sweating causes losses of water and electrolytes. Merck notes that horses worked hard in hot weather are at risk for salt deficiency, and that plain water alone may not fully support rehydration in heavily sweating horses. Balanced equine electrolyte products can be useful for some horses, but plain water should always remain available.

The right plan depends on workload, diet, climate, and the individual horse. Some horses do well with free-choice salt plus careful water access, while others in endurance, eventing, racing, or repeated summer work may need a more structured electrolyte plan. You can ask your vet which product, dose, and schedule fit your horse.

Not every horse handles heat the same way. Horses with obesity, poor fitness, anhidrosis or reduced sweating, recent transport stress, illness, or a history of heat intolerance may struggle sooner. Merck also notes that obese horses and ponies have decreased heat and exercise tolerance.

If your horse is a poor sweater, management often needs to be more proactive. PetMD describes anhidrosis as a condition where horses do not sweat appropriately and may show puffy breathing, prolonged high temperature after exercise, lethargy, and exercise intolerance. These horses often need cooler exercise times, stronger emphasis on airflow and shade, and closer monitoring.

Call your vet promptly if your horse is not recovering normally after exercise, is breathing hard at rest, has tacky gums, seems weak, stumbles, stops sweating in hot weather, or has a temperature that stays elevated. These signs can overlap with other serious problems, including colic, tying-up, infection, or transport-related illness.

See your vet immediately for collapse, severe depression, inability to stand, neurologic signs, or suspected heat stroke. Moderate to severe dehydration may require veterinary assessment, bloodwork, and oral or IV balanced fluids tailored to the horse's needs.