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Caring for horses during hot weather

Quick facts

  • Provide shade, airflow (e.g. fans) and free access to clean water during hot weather.

  • Avoid riding your horse when the air temperature and relative humidity combined exceed 150.

  • To cool an overheated horse, repeatedly sponge it with cool water and scrape it off right away. Repeat this until the horse is cool.  If near a water source, spray the horse continuously with cool water, making sure to scrape off any excess water when finished.

  • Contact your veterinarian right away if you suspect your horse is having a heat stroke.

  • Hot weather can bring diseases like West Nile Virus and Potomac Horse Fever.

You must provide extra care to your horse during hot weather to:

  • Reduce their stress

  • Maintain their health

  • Maintain their well-being

Sweating horse
Horses naturally cool themselves by sweating.

Sweating, natural cooling

Horses normally cool themselves by sweating. The sweat evaporates from the skin surface and causes a cooling effect. Less sweat evaporates during times of high humidity. Table 1 shows how air temperature and relative humidity affect the horse’s ability to cool itself.  Horses can acclimate to hot and humid weather conditions; however, the below guidelines can help reduce (or avoid) heat stress in horses.  

A horse that is working hard in a hot environment can lose 2 to 4 gallons of sweat per hour.

Table 1. How air temperature and relative humidity affect horse cooling

Air temperature (F) + Relative humidity (%) Horse cooling efficiency
Less than 130 Most effective
130-150 Decreased
Greater than 150 Greatly reduced
Greater than 180 Condition can be fatal if the horse is stressed

Keeping your horse cool

Overheating can result from the following:

  • Hot weather

  • High humidity

  • Poor barn ventilation

  • Prolonged exposure to direct sunlight

  • Excessive work

  • Transportation

  • Obesity

Summer is a common time for heat-related issues but unexpected warm weather can add to overheating, especially if horses are out of shape and have long, thick coats. Here are some tips to keep your horse cool and comfortable during hot weather.

Hosing down a horse
First, hose down the horse.

Cooling an overheated horse

To cool an overheated horse (rectal temperatures above 103° F):

  1. Spray (with a steady stream of water) the horse’s head, back, neck, rump and legs with cool water.

  2. Spray and scrape the water off right away. Water can act as insulation and increase the horse’s body temperature if you don’t remove it.

  3. Repeat this continuously until the horse is cool.

Woman scraping water off a horse
Then, scrape the water off right away.

You can add ice to the water to speed-up cooling for very hot horses (rectal temperatures above 105 F). Research shows using ice to cool a hot horse is safe. Ice baths reduce core body temperature and lower heart rates after hard exercise. Horses were also found to trot more freely after an ice bath.

Don’t directly apply ice water over the hind end (large gluteal muscles). Focus on areas where the blood vessels are more prominent: head, neck, back and rib area.

Don’t place a sheet or blanket on the horse when trying to cool it. Blanketing will block water evaporation from the skin. Don’t blanket during hot and humid conditions.

Effects of heat on horses

Skin tent test
A skin tent test can check if your horse is dehydrated.

Prolonged exposure to high temperatures can result in:

  • Heat stress

  • Heat stroke

  • Problems such as dehydration, muscle spasms and colic


Acclimating horses to the heat

We recommend a 15 to 21 day acclimation period for horses from cooler or drier climates traveling to compete or reside in hot, humid climates. Acclimation increases the horse’s tolerance to heat and exercise. You should still monitor the horse during training and competition in hot and humid climates.

Warm weather infectious diseases

Hot weather brings an increased risk of infectious diseases that involve arthropods transmission to horses. Two important diseases in this category are West Nile virus (WNV) and Potomac Horse Fever (PHF). WNV causes neurologic signs and muscle trembling, killing almost a third of the horses that develop signs. Mosquito numbers often soar in late summer, as larvae hatch from warm water pools.

Horse owners can do 3 things to lower the risk of WNV infection:

  • Eliminate or treat all standing water in their horse's environment to discourage mosquito hatching.
  • Minimize the likelihood of mosquito bites by keeping their horses indoors during prime mosquito feeding times (dawn and dusk) and protected with repellants.
  • Ensure their horses are well vaccinated against WNV. This may include a late summer booster vaccination, in addition to a vaccination in the spring.

PHF cases are more frequent in late summer and are characterized by fever, laminitis and often, diarrhea. Horses can be infected by drinking contaminated water, or by ingesting feed that has been contaminated by insects from aquatic environments. PHF resembles several other diseases so immediate veterinary care and diagnostic testing are strongly recommended.

Krishona Martinson, equine Extension specialist; Marcia Hathaway, professor of Animal Science, College of Food, Agriculture and Natural Resource Sciences; Christie Ward, DVM; Roy Johnson, Cargill Animal Nutrition

Reviewed in 2018

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