I had heatstroke twice and it is not very pleasant. What helped me was staying in a cool dark room, and licking tiny amounts of salt and sips of water.
But of course it's different for dogs as they can't sweat to cool down as humans can. And of course they are wearing a fur coat to start with.
But of course it's different for dogs as they can't sweat to cool down as humans can. And of course they are wearing a fur coat to start with.