Sometimes they are having so much fun that they forget to come in out of the sun and rest, so we have to make sure they don't stay in the sun very long. You could put a kiddie pool out with a couple inches of water, you can also put dog sunscreen on them, and sunblock on the face and ears,
http://vetmedicine.about.com/od/dise...screens.htmand feed them barley. Barley is the only food that cools the inner core of humans and dogs. There is pearled barley and quick cooking barley. I cook the barley in a beef or turkey broth so it has a better flavor.
Try to limit walks to either early morning or evening when it's cooler outside, and if the asphalt is hot, then try sneakers for them. The ones that have tiny air holes to keep the paws cooler.