06/09/2026
It's going to be another hot one again this week: A good rule of thumb when assessing how the heat will affect your workout is to measure the Heat Stress Index (HSI). If the sum of the temperature in degrees Fahrenheit plus the percent of humidity totals less than 120, all systems are "go.” If the sum is greater than 150, particularly if humidity contributes to more than half of this number, your horse’s natural cooling mechanisms will be compromised. You should consider lowering the intensity of your workout, shortening the length of time, or riding later in the day. If the HSI is greater than 180, a horse cannot regulate his core body temperature naturally, so he should not be forced to work. For instance, if it is 100 degrees with 80 percent humidity, leave your horse in a shaded paddock with plenty of cool, clean drinking water and go have a cold drink yourself.
