Hong Kong summers can be extremely uncomfortable when humidity levels  become very high. Not only unbearable for us, but spare a thought for Chow Chow, Hong Kong summers can be extremely uncomfortable when humidity  levels a shaggy Pomeranian or fluffy Persian. Not only that, have you seen a dog or cat sweat  before? 
Actually they do sweat,  but it is limited to the underpads of their feet.  Sweating is one good way to keep your body temperature under control.  As your sweat gets evaporated away it helps to draw the heat away from you. If your sweat glands are only available on your feet it is hardly an efficient way to cool your body down.
of rapidly breathing helps to draw hot air away from them.  The movement of air will also help draw the heat from the vascular blood supply of their tongue. This process has it's limits though.  You can only breath rapidly up to a certain rate before your breathing becomes too shallow to be of any us Generally dogs and cats will try to cool themselves down by panting.  The acte and your excessive muscle movements also contributes to the production of heat as well.  
Heat stress comes about when your body is unable to stop the ongoing rise in body temperature.   In extreme circumstances organ damage will occur has the body literally begins to burn up.  If body temperature rise to 105F or 41C organ damage will lead to organ failure and can be fatal! Annually we will see many cases of heat stress to varying degrees.  The cases that lead to death can be very stressful to deal with for all parties.  Seeing the dog or cat suffer is very unpleasant.  From this experience prevention is definately a better option over cure. Make every effort to keep the living space for your pet as well ventilated as possible. Do not assume that if your pet is away from the sun, that they are safe from heat stress. A still, non-ventilated room will be very stuffy. If your pet is active for any reason; perhaps playing or overly excited about something, it's body temperature can rise very quickly under these conditions. Your pet dog still needs it's exercise even during the summer months. You must be extra cautious in preventing your dog from over exerting itself. Try to avoid prolonged outings during the hottest time of the day.  Midday is generally not a good time to go out for long runs! Try to arrange early morning or evening walks when the weather has cooled down a little. You may have a dog who happens to be very excited and happy when it comes their daily exercise.  They will be very active whether it is a hot or cold day.  You need to monitor these dogs very carefully.  If the dog is panting excessively it might be time to settle the dog down. If it is off the lead it would be a good time to put the lead back on so you have better control. It would be a good idea to carry water with you. A good way to cool down is to have a good drink of water. If the dog is near water it may be a good time for the dog to go for a swim to cool that body down.