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.
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° 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 thermoregulation 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+ Thermoregulation has been lost. Do not exercise. Working a horse in these
conditions can be dangerous, even fatal.