Do you mean heat tolerant or drought tolerant? There are no grasses that will stay green all summer in your hot climate without irrigation. Without water, there are a few that will go dormant, then re-emerge when the weather cools off. Bermuda, zoysia, buffalograss, and even tall fescue fall into this category. Plant any of these and water them if you want them to stay green all summer, or let them go brown if you dont' want to use the water. Avoid bluegrass, ryegrass and St. Augustine.