TEMPERATURE: Heat Index


We know our horses can overheat in summer conditions, but how much is too much? As the temperature and humidity rise, we need to be vigilant about protecting our equine friends from heat stress.


The Heat Index is a tool that provides good general guidelines for working your horse. It is easy to use and a veterinary accepted guideline for heat and the horse.


To use the index, add the current temperature (in Fahrenheit) and the relative humidity (in % RH) together. The total number determines the conditions. For example, if it is 77 degrees out and the relative humidity is 65%, add them together for a total of 142. When you have your total, see the table for recommendations.


If Temp °F + % Relative Humidity =


120 or less Your horse’s cooling system is functioning very effectively.

120-150 Cooling efficiency is decreasing through this range. Horses will sweat up with work, so

make sure they have a chance to rest and cool off.

150-180 Temperature regulation is greatly reduced and heat stress is more likely, use caution and

provide ample cool down, rest, and recovery.

180 or more Thermoregulation has been lost. Do not exercise. Working a horse in these conditions can

be dangerous, even fatal.