A number of things can cause your laptop to run warmer than it should, and none of them will be doing your laptop any favors. You can avoid damage to your laptop by understanding what causes a laptop to overheat, and taking the necessary precautions to avoid it.

Poor Ventilation

Ventilation is vital to a cool-running laptop. Blocked vents or blocked fan intakes and outputs will quickly cause a laptop to overheat.

Temperature

Using a laptop in hot environments, such as hot weather, factories, or near heating vents, can cause it to overheat as well. Limit such exposure by using a laptop in room temperature environments or using additional cooling as necessary.

Taxing Programs

Programs that tax the laptop's processor and graphics card cause more overheating than average usage. Examples of these types of programs are games, compilation programs, virus scans, and other programs that use the processor and/or the graphics card to near full capacity.

Consequences

Component damage is the most likely problem that can occur from a warm laptop, and you may eventually need to have damaged parts repaired or replaced. Aside from that, a burnt lap and, supposedly, sterility are the physical problems you'll have to keep in mind.

Precautions

Many solutions are available, but the best precautions to take in order to avoid an overheating laptop are to never block the laptop's ventilation and possibly add a cooler or allow a fan to blow on the laptop; to never operate a laptop in extreme temperatures; and to ensure that your laptop is capable of running the programs installed on it. For instance, most laptops are not meant to play graphics intensive games because they will overheat.

Source:

Laptop Overheating Website: Lap Overheating