If your horse has not been in regular work or you are unsure about a new mount’s work history, begin your summer workouts slowly with approximately five to 10 minutes of trot only. Increasing your total workout time by five minutes each week, as well as increasing the intensity or speed at which you ride, will give your horse time to acclimate to the heat and humidity. | Photo: iStock

We all long for warmer weather and the longer rides summer affords. But heat and humidity are major concerns for rider and horse since heat-related illness can be dangerous–even fatal. Horses have efficient natural thermoregulatory systems to cool themselves, but sometimes they are overwhelmed and cannot compensate for the heat. Hyperthermia or heatstroke results when your horse is unable to control his internal temperature and it starts to rise.

Signs of heatstroke are elevated respiratory rate–40-50 breaths per minute (normal: eight to 16)–that does not slow when at rest; a heart rate over 80 beats per minute (normal: 36-44 beats per minute) that does not slow down after a few minutes of rest; elevated rectal temperature over 103°F (normal: 99-100.5°F); lethargy; and/or profuse sweating or absence of sweating altogether. If left untreated, hyperthermia can cause death. It is neither the heat alone nor the humidity alone that is concerning, but the two factored together. Most researchers define high heat as over 86°F and high humidity as 80-85%.

Hyperthermia can occur when one of these three things are present: inadequate (fitness) conditioning, extreme hot and humid conditions, or a weakened thermoregulatory system