Keep him wellwatered

Your horse’s natural cooling system can be overwhelmed by heat and humidity, leading to dehydration and even heatstroke. When temps soar, moderate his work schedule and offer more frequent water breaks. Check hydration by pinching the skin on his neck or shoulder, then letting go—the skin should snap right back. Follow hydration basics (below), and ask your veterinarian about the advisability of electrolytes to replenish potassium and sodium. Ideally, keep your horse from reaching even 2 percent dehydration (left).

A 1,000-pound horse may drink as much as 10 gallons of water a day, and a great deal more when worked.