Spice has been like this,with the heat of the last few days,me too :D we both sit in front of the fan in the living room after short walks to cool off,then she goes into the garden snuggles down into her dugout under my tree fern

and sleeps for ages.
She is eating o.k and her water bowl is topped up reguarly.Also we have bought an extra fan for the rear of the car,which plugs into a socket in the boot area and runs off the car battery in addition to the ac. and we take a small spray bottle of water on walks with us as she loves being 'misted' with it.In fact if I get the hose out to do my plants that I have just put in,she is right there! jumping in and out of the spray! so a pile of doggy towels are at every door!
If you have any doubts though as to his health whatsoever I think it is wise to check it out with a pop-in visit to your local vet.
Jacqueline. :)