Dogs do not actually have sweat glands (to regulate body temperature and cool themselves) like a lot of other mammals.  Instead they cool their bodies by panting.  "Panting is the normal process by which dogs lower their body temperature.  This is accomplished by the evaporation of water from the mouth, tongue and lungs, and by the exchange of cooler air for the warm air in the lungs".

     Although dogs do have small sweat glands in their feet, they are of little help in cooling a dogs temperature down.  Sweating through the pads of the feet is more  noted when a dog is in a very fearful or stressful situation. But a dog will seek out a cool surface or ground cover to stand or lay on also to cool themselves as the blood in their pads cools standing on a cooler surface and circulates back through the body.  Same with laying down on a cooler surface.  The blood next to the skin is cooled and helps bring their temperature under control.