Long, sunny days mean more time to spend outdoors with your horse. Just like humans, horses can sweat to help manage their body temperature in the heat. But even with their ability to sweat, they can suffer from heatstroke, a life-threatening medical emergency.
When the temperatures rise over 80 degrees Fahrenheit or when the heat index, or outdoor temperature plus relative humidity, is over 150, you’ll need to keep a close eye on your horse and limit their physical activity.

What Is Heat Stroke In Horses?
When it’s hot out, one of the ways your horse naturally regulates their internal body heat is through vasodilation. This is when blood vessels close to the surface of their skin dilate, helping them release body heat through their skin into the surrounding air.
But when your horse is overheated, this process fails to maintain a normal body temperature. Meanwhile, the increase in circulation of blood to their skin diverts circulation from their digestive tract, kidneys, and ultimately, their brain. In severe cases, heat stroke leads to organ failure and death.

Symptoms Of Heat Illness and Heat Stroke
If you monitor your horse for signs of heat exhaustion, you can intervene before it progresses to heat stroke, which is always a medical emergency.

Signs of heat exhaustion include:

• Excessive sweating
• Rapid heart rate
• Rapid breathing
• Muscle spasms
• Decreased urination
• Dehydration - use the skin tent test to check

Heat exhaustion can quickly progress to heat stroke. Sweating may stop, the horse may stumble, collapse, experience convulsions, or even go into a coma.
If you suspect your horse is experiencing heat exhaustion or a heat stroke, call your veterinarian. In the meantime, move your horse into the shade, mist or spray them with cool water, and keep them in front of a fan, if possible.

Preventing Heatstroke in Horses
Though any horse can suffer from heatstroke when exposed to extreme heat and/or when overexerted, foals, overweight horses and those over four years old are at an increased risk.
Horses generate a lot of body heat as they chew and digest their feed, making them more prone to overheating up to four hours after a meal. Feed your horse 3-4 hours before and at least two hours after physical activity. Give your horse frequent opportunities to drink water before, during, and after a ride.

Horse Heat Stroke Precautions On The Road
If you must trailer your horse during the summer, aim to make your journey before or after the hottest hours of the day, around 10AM to 4PM, though these hours can vary.
Once stopped, never leave your horse unattended in their trailer. Just like a hot car, a parked trailer can exceed 130 degrees Fahrenheit.