How to keep your pets cool TheHumane Society of America and ASPCA warn pets can also get sick or die from heat-related illnesses. Animals with flat faces/short muzzles — Persian cats, pugs, boxers, shih tzus, etc. — can't pant as effectively as other breeds. They and elderly or overweight animals, and those with heart or lung diseases are especially vulnerable to heat-related illnesses. To help protect animals: Keep pets indoors and in air conditioning as much as possible. Never leave a pet in a car. Even leaving them in an open vehicle for a couple of minutes can be dangerous in high heat.