Owning a pet means being responsible for its health and welfare. For advice on all your animal concerns, speak to your veterinarian. Heat stroke happens when your pet’s body can’t cope with the external heat, leading to illness, organ failure and even death. Humans sweat to help regulate their body temperature, but dogs don't have prominent sweat glands, so they rely on panting to cool off. Cats will sometimes groom themselves as a cooling mechanism but may also pant.