I think there is global warming. The signs are there. Heatstroke is not something you would normally consider for your cat. I think it is rare but it can happen under certain specific circumstances and it is important to protect against those circumstances and to recognise the signs of feline heatstroke as it will facilitate rapid action.
Cats have poor mechanisms for heat dissipation
The problem with cats is that they don’t tolerate high temperatures as well as people and they don’t sweat like people. Therefore they can’t cool down as well as people. They sweat minimally through their paws and remove heat from their bodies by panting (rapid breathing to exchange warm air for cool air). Cats who are overheating also cool themselves down by licking their fur. The saliva evaporates which is a cooling mechanism. However, if the air temperature is similar to the body temperature this method of cooling is ineffective.
It seems to me that a set of special circumstances can come together to cause heatstroke in a cat. The obvious example would be a cat in a carrier inside a car with the windows shut on a warm or hot day. The inside of the car heats up rapidly under these circumstances and may do so to a dangerous point without the owner being aware of the danger. If you add into the mix a cat with an airway disease which is a barrier to dissipating heat through rapid breathing or conditions which interfere with efficient breathing then you perhaps have the circumstances under which heatstroke can occur. Note: carriers which are meshed on all sides provide a better airflow and the car window can be open to provide ventilation to the cat inside. The cat carrier at the top of the montage below is the type I am referring to.
Other issues would be long-haired cats and cats whose anatomy leaves them predisposed to breathing problems such as the flat-faced Persian. That breed would be a typical example of a problem cat in terms of heat exhaustion under specific conditions. These cats are banned from some airlines because of their breathing problems.
The symptoms of heatstroke in a cat begins with noisy breathing which is frantic and rapid. The mucus membranes and tongue are bright red and the saliva is sick. The cat might vomit. Their temperature as measured with a rectal thermometer may be over 106°F or 41°C. The condition should be confirmed through taking their temperature.
The big issue here at this point is that without immediate input from the cat’s owner they might die. It is that serious. Emergency measures must take place rapidly once the owner has diagnosed the symptoms.
The advice that I have in a book on the subject (written by four American veterinarians) is that the cat caregiver has to take a rectal temperature check every 10 minutes. In mild cases of heatstroke, moving the cat to cooler environment such as an air-conditioned building may be enough. But if the cat’s temperature is over 106°F (39.4°C) or if she is unsteady then you have to take action including applying wet cold towels to the cat’s groin and armpits as well as the head. Alternatively you can immerse the cat’s body in cool water. The target is to reduce the cat’s temperature to 103°F.
There are alternative ways to cool down a cat with heatstroke. You can wet the cat with a garden hose or use ice packs applied to their head and groin area. Once the temperature drops to below 103°F you can stop the calling process. You do not want to cause hypothermia.
Get veterinarian involved
You must telephone your veterinarian and get them involved as soon as possible. If you delay health issues such as kidney failure and cardiac arrhythmias and seizures can occur. A complication is that the throat may swell up which exacerbates the problem. This can be fixed with a cortisone injection by your veterinarian.
Proactive and aware
The big issues which are raised is that this is about awareness and taking preventative action. Cars are dangerous places in hot weather and real caution needs to be taken in that regard. If your cat has an airway disease or impaired breathing they are more vulnerable. Within the home there should be shady and cooler areas where a cat can rest to maintain body temperature.