Laptop computers are delicate, expensive and sensitive pieces of high technology. While it is easier to avoid obvious laptop destroyers like water and fire, extreme temperatures, such as those in a hot car, can sneak up on you and warp your computer before you know it. Even though you should always try to keep your laptop out of a hot car, if you have to there are a few practical things you can do to protect it.
Make sure the laptop is shut off all the way. Even in power-saving mode, it still generates a little bit of heat. You want to avoid creating any more heat than is already in the car. You can burn out the motherboard and hard disks if they constantly absorb more heat than they can handle.
Keep the laptop out of direct sunlight. Cover it with a white towel, or something bright in color, to reflect sunlight and create a buffer between it and the heat in the car. Avoid covering it with anything dark in color, as it will absorb heat and transfer it to the laptop, trapping the heat and creating a hotter area than if it were left completely exposed.
Wait for the laptop to cool down after shutting it off before you leave it to sit in a hot car. Again, excessive heat beyond what is already generated by the computer can cause serious damage. Consider the risks of leaving a laptop in the hot sun before actually doing it. You run the risk of losing an expensive tool, probably used daily, not to mention a lot of data.