There are a few things you can do to help out any outdoor pets you might have. For long haired breeds of cats and dogs, one solution is summertime grooming - get them a haircut! But this is only a temporary solution and it doesn't address the problem for their shorter haired cousins.
One ingenious way of keeping your pets cool as a cucumber in the summertime is to invest in a kiddie pool. Yes, the same plastic pools that you can buy at the store. FiIl it up with about 3-4 inches of water to give those pets some relief! Placing it in whatever shade you can muster helps a lot as well. Dogs, and even cats, that don't like the water will get in to cool off when it gets really hot. It also becomes an additional source of water for them if they are feeling parched.
Don't forget to change it every other day or so, to keep the water fresh and clean! They'll thank you for it.