Summertime heat and humidity can be dangerous to horses. Horses can and do survive in hot environments primarily through sweating, as well as other thermoregulatory mechanisms. However, if their body temperatures get too high, horses can suffer heat exhaustion or heat stroke.

If the heat stroke is severe enough, it can lead to death. Therefore, it is important for any horse owner to understand how best to manage their animals during the hottest times of the year.

The primary way horses reduce body heat is through sweating. Horses can produce over 3 gallons of sweat an hour. Thus, water is the primary consideration when managing any horses in hot weather. Water is critical for regular body function, digestion, and thermoregulation. A horse should have access to free-choice water 24 hours a day because, on average, they will drink 10 gallons of water per day. Of course, that will vary with exercise intensity, type of forage fed, and weather. For example, in hot temperatures, individual horses can drink up to 20 to 25 gallons of water per day.  It is also very important to always ensure your horses’ water buckets or troughs are always full and filled with clean water. If your facility has an automatic water system, check it daily to ensure it is functioning properly.

When sweating, not only does the horse lose water, but also important electrolytes. The major electrolytes include the minerals calcium, phosphorus, sodium, potassium, and magnesium. These are also very important for proper body function. Thus, it is important to ensure a horse receives adequate daily nutrition to replenish their electrolytes, especially if sweating or exercising in hot and humid environments. Forage can adequately replenish potassium for most working (sweating) horses. However, forage alone is not adequate to replenish all the electrolytes in moderate to hard-working horses. Thus, electrolytes usually can be replenished through a well-formulated feed or by feeding an electrolyte supplement.

The average body temperature of a horse ranges from 99 to 101 °F. It is generally thought that any body temperature above 104 °F can be dangerous for a horse if it is maintained for too long a period. Exercise is primarily the cause of elevated body temperature, especially in a hot and humid environment. Any body temperature of 107 °F and above is generally considered the death zone for any horse and owners should seek immediate veterinary attention if a horse gets this hot and cannot be cooled down quickly.

To measure the body temperature of a horse, you can use a digital thermometer by inserting it in the animal’s rectum. However, use caution when inserting the thermometer. To safely do this, stand to the side, lift the horse’s tail and then slowly insert the lubricated thermometer, with only two thirds of the thermometer inserted. After the digital reading, slowly take the thermometer out.

An easy way to check to see if your horse is dehydrated is through a skin pliability or skin pinch test. This can be done by gently picking up the skin or pinching it near the neck or shoulder of the horse.


In a well hydrated animal, the skin should immediately bounce back. If the skin tents or slowly return to its normal position, this means the animal is likely dehydrated and needs water.

Heat exhaustion can be a problem for horses kept or exercised in hot and humid environments. This can be identified if the horse’s temperature stays elevated above 104 °F for more than 20 minutes after the cessation of activity. Other signs could include:

  • Profuse sweating, with sweat getting sticky
  • Rapid breathing and heart rate
  • Gums become discolored or dark
  • Listless, head down, appears weak

If you suspect your horse is experiencing heat exhaustion, you should immediately move them to a shaded area. Then cool your animal off with cold water, with focus on the fleshy areas like the shoulders, loin, and hind end. You should scrape off any excessive sweat or water and use a fan if possible. Finally, offer small amounts of water, 2 to 3 gallons, every 30 minutes. As mentioned above, if the horse’s body temperature does not decrease, then seek immediate veterinary attention.

Finally, here are some other tips to help your horses stay cool during hot and humid days:

  • Exercise horses during the coolest times of the day
  • Wash down with cool water, especially after exercise
  • If horses are kept in a barn or stalls, ensure there is proper ventilation - provide fans if needed
  • Provide shade for turned out horses either by trees or shelters
  • Provide salt/mineral licks or consider supplemental electrolytes

Overall, water is always the main concern for any horse kept in a hot and humid environment, followed by electrolyte intake. Horses generally do well in hot and humid environments if their owners are aware of the dangers and take the above actions.
 

Chris J. Mortensen, Ph.D.