08/21/2026
Did you know that a horse can become overheated enough to cause neurological injury—if he survives?
Severe overheating can progress to exertional heat illness or heatstroke, a potentially life-threatening condition in which the horse’s core temperature rises to dangerous levels and his normal cooling mechanisms can no longer keep up.
Is the Horse Essentially Being “Cooked”?
In very severe hyperthermia, that is actually a useful analogy.
The body’s cells and proteins can only function properly within a certain temperature range. When body temperature becomes extremely high, heat begins interfering with normal cellular function and can directly damage tissues.
At the same time, other things are going wrong. Dehydration reduces circulating blood volume, circulation may become compromised, and less blood may reach important organs, including the brain. Severe heat illness can also trigger widespread inflammation and abnormalities in blood clotting.
The damage can therefore come from a combination of extreme heat, impaired circulation, inflammation and disruption of normal cellular function.
The nervous system is particularly vulnerable. Reduced blood flow to the brain can contribute to inadequate oxygen delivery, swelling, disruption of the blood-brain barrier and injury to nerve cells.
Neurological Signs Can Develop
As heat illness becomes more severe, a horse may show:
* Changes in behavior or awareness
* Disorientation
* Stumbling or incoordination
* Weakness or collapse
* Loss of normal reflexes
* Seizures or convulsions
* Stupor or coma in the most severe cases
Some horses survive a severe episode and recover completely. When overheating is sufficiently severe or prolonged, however, neurological injury and damage to other organs may persist even after the horse’s temperature has returned to normal.
Heatstroke Can Affect the Whole Body
The brain is only one of the organs at risk.
Severe heat illness can also lead to:
* Severe dehydration
* Electrolyte and acid-base disturbances
* Gastrointestinal injury
* Circulatory problems
* Widespread inflammation
* Abnormal blood clotting
* Kidney, liver or muscle injury
* Multiple-organ failure
This is why severe heatstroke can continue to be dangerous even after the horse has been cooled.
What Increases the Risk?
Heat illness becomes more likely when a horse exercises in hot, humid conditions because exercise generates large amounts of internal heat while the environment makes that heat harder to lose.
High humidity is especially important because it reduces the effectiveness of evaporative cooling from sweat. Poor airflow, intense or prolonged exercise, dehydration, lack of acclimatization, heavy body condition and inadequate cooling during or after work can all increase the risk.
A horse can overheat surprisingly quickly when several of these factors occur together.
An Elevated Temperature After Exercise Is Not Automatically Heatstroke
A horse’s body temperature normally rises during strenuous exercise, particularly in hot and humid conditions.
The greater concern is severe or prolonged hyperthermia accompanied by signs that the horse is no longer coping normally, such as altered behavior, weakness, incoordination, collapse or other signs of systemic illness.
A re**al temperature around 105–106°F (40.6–41.1°C) or above is particularly concerning, but temperature alone does not tell us how much injury has occurred. How high the horse’s temperature rises, how long it remains elevated, his hydration and circulation, and his individual response all matter.
Suspected heatstroke is an emergency. Begin actively cooling the horse immediately and contact your veterinarian.
https://koperequine.com/31-things-every-horse-owner-should-know-about-horses-and-heat/
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