wont start when hot outside????

Here is a little pondering question for you all. Yesterday my friend went out to his vehicle and tried to start it. All it would do was fire one time and shut down. He said it happened yesterday also. All we did was open all the drivers door and the hood. So the question is what is getting to hot not to let the vehicle start when hot out. It is an 03 with a 5.3 in it. The temp those to days was 105 to 110 when he tried to start it. Anyone have any suggestions much appreciated.