Q: How do you tell when it’s too hot to ride your horse?
A: I admire you for being concerned about your horse’s safety and comfort when the thermometer climbs! As you probably know though, it’s not just rising temperature that puts your horse at risk; it’s other factors such as high humidity, lack of airflow, and direct sun rays that combine to make the outdoor environment – let alone exercising – uncomfortable if not downright dangerous.
That’s because horses, like humans, cool their bodies primarily through the evaporation of sweat. However, if the air is already high in moisture – like it is when the humidity level is high – then this process doesn’t work very well. And if there’s no air moving or no shade available, then a horse can overheat even more quickly.
Two more things to factor into the equation: is your horse is acclimated to the weather and is he conditioned for the exercise? A horse from a dry, cool northern state that is transported to a hot, humid southern state is going to need about three weeks to become accustomed to the change in temperature and humidity. This is why a rider from Texas or Florida might think nothing of a workout or competition on a 90º F day while a rider from Washington or Oregon might give their horse the day off or scratch from a show. Likewise, a horse that’s already fit is going to tolerate exercise on an exceptionally warm and muggy day better that a horse who’s just been standing around and hasn’t become efficient at cooling.
That said, there is a “Rule of 150” that many people rely on as a gauge for when they should take it easy and when it’s safe to exert themselves outside. Basically the “rule” is if you add the temperature to the humidity and it’s above 150, you should think twice about exercising during that time (examples would be 90º F and 60% humidity, or 80º F and 70% humidity). And if there’s no breeze and no shade, the body can get overwhelmed pretty quickly.
In essence, use common sense, make sure your horse always has fresh water available (even right after a workout), and don’t be afraid to bring his body temperature down quickly with cold water or even ice (yes, right after a workout). Oh, and now would be a good time to provide some electrolytes!