It's not only my garden that is struggling in the heat, but our flowers are really gasping for breath too. Since we have a raised deck that goes all around our house, my wife likes to hang flower baskets under there. Normally, petunias do well, but the combination of the hot wind beating them to death and late afternoon searing sunlight has them struggling. Petunias are great summer plants if they can get a good root system established in the first warm months, but they sure don't like to be blown around by the wind. If there is a formula that works, we haven't found it.
The best plants so far are the marigolds in a flowerbed that is protected from the south wind and gets only about 2 hours of direct sunlight during the day. Also doing well are caladiums and coleus plants in beds up under the deck where they are partially protected from the wind and get no direct sunlight. Even so, they need water often. I have replaced my tulips from early spring with zinnias in a bed that gets every ray of sun. I put 15 gallons of water on that 10' round bed every other day when it is hot like now. One thing for sure, one watering per week is not enough. If we don't lightly water the flowers every other day, they start to really wilt. So when it is this hot and windy, it seems I spend all my time watering the garden, the yard, or the flowers. Oh yes. . . we have to keep fresh cool water out for the kitties too.
EDIT: And speaking of kitties. . . our catfish are spawning. Our pond has cleared up for the first time ever since I cleaned it out. The water is so clear we can watch catfish coming into the shallows and making their spawning beds. We sat yesterday and watched as about twenty catfish circled the pond searching for good places to spawn.