Like many outdoor surfaces, artificial grass in direct sunlight on a very hot day may become uncomfortably warm to stand on. It is direct sunlight that will warm up your synthetic turf, so any area in part or full shade should stay nice and comfortable. If you want to use your area bare footed on a hot day, and testing the temperature you have found that it is too warm to stand on, you can give it a very light sprinkle of water with the hose to cool it instantly.