Heat Stroke can easily be fatal and is a result of lack of ventilation, water, or overheating on hot days.

As many animal lovers have pointed out about a million times before - do not leave your animals unatteded in cars during the warm season! Even with widows open a crack the temperatures might easily reach 150+ degrees when parked in the sun.

Older or overweight dogs are more susceptible to heat strokes when not enough shade is provided on sunny and hot days (we are not talking cars here, I mean yards, during walks, etc.).
Don’t over-exert your dog, neither young nor old, in the heat of a summer day! Avoid heat stroke by providing enough shade, and fresh water (add a few ice cubes) all the time.

Symptoms of head stroke are heavy panting, high pulse rate, vomiting and, eventually, coma. The animal’s body temperature has to be brought down immediately. Either submerge it in cool water, hose it down, or wrap it in wet sheets. Rush to the veterinarian.