Heatstroke is a preventable but often fatal condition in dogs, most commonly caused by being left in hot cars, causing significant suffering that is entirely avoidable.
Heatstroke causes suffering rapidly and escalates to irreversible brain damage and organ failure within a short time. Dogs cannot sweat effectively and overheat quickly in confined hot spaces. Brachycephalic dogs have additional airway compromise that worsens heat management. The key welfare message is simple: never leave a dog in a car in warm weather, even briefly. Prevention is completely achievable; treatment of severe heatstroke has limited success.