There are a few things that you can do to make sure that your grass stays cool in the hot summer months. If you want to use your area bare foot on a hot day and notice that the grass is a bit warm, you can give it a very light sprinkle of water with the hose to cool it instantly.
You will find that shaded areas keep the grass very cool. Only when the grass is in direct sunlight for long periods of time, on a really hot day, will you find that it will be a little warm.