Heat stroke is a life-threatening emergency in dogs. It kills more rapidly than almost any other acute condition and is entirely preventable. Leaving a dog in a car is the single highest-risk scenario.
Heat stroke causes cellular damage to multiple organ systems simultaneously — brain, kidney, liver and gut. Survivors may experience permanent organ damage. The suffering involved is extreme and acute. Prevention through never leaving dogs in cars, avoiding exercise in the heat of the day, and always providing shade and water is straightforward and the only responsible approach.