Lots of people confuse heat-hardy with drought-tolerant. There are many plants that can tolerate the heat of the summer as long as they are given a good, long and frequent drink of water. Plants native to the desert will tend to be more tolerant of dry conditions than those from a tropical environment. For advice on which plants do the best in the summer in your area, consult with your local cooperative extension office, as they have a lot of area-specific information.
The shrimp plant is an evergreen shrub with interesting bronze-colored flowers. This plant grows well in pots as well as a shady spot in the garden. Give it an application of all-purpose fertilizer in the fall, and water it when the top three inches of soil is dry. Other than that, it's not a particularly finicky plant. It's hardy to USDA Zones 9 to 11.
Society garlic, which is hardy to USFA Zones 7-11, does great with full sun and lots of heat, as long as you water it twice a week. Blooming with pink or lilac flowers, on stalks that can reach two feet in height, this is a fast growing plant. An attractive companion for the society garlic is the hibiscus.
Orange Cape Honeysuckle
This is an evergreen vine or shrub that behaves well in the heat and full sun. It is very fast growing, drought-tolerant and deer-resistant. Late in the summer, when all the other flowers in the garden are dropping, the orange cape honeysuckle begins to bloom with trumpet-shaped orange flowers. Hardy to USDA Zones 9 to 11.
The hibiscus, which is hardy to USDA Zones 10-11, rewards the gardener in the heat of the summer with beautiful, tropical flowers. This plant needs full sun and extra water when it is particularly hot. The Amour variety is especially tolerant of the heat.