Test Laptop Temperature

Answer: Using a free monitoring program, you can check your laptop's internal temperature to see if it's running too hot and in danger of overheating.

The biggest clue that your laptop is not running at an ideal temperature is if you're experiencing any symptoms of overheating. But most laptops naturally run hot, so a system utility that can access your laptop's internal temperature sensors can help you decide if you need to take steps to cool your laptop down further.

You can look up temperature specifications for your specific laptop's Intel or AMD processor, but most CPUs' maximum temperatures are around 100° Celsius (212° Fahrenheit). Before you get to that upper limit, though, your laptop will likely have all sorts of performance problems and may be shutting down randomly on its own. Optimal operating temperature is 50° Celsius (122° Fahrenheit) or below, according to the SpeedFan temperature monitoring program, though newer processors may go comfortably higher to around 70° Celsius (158° Fahrenheit).
Sources: Intel, AMD, Kioskea.net

Several free temperature monitoring programs are available that can show you the CPU temperature as well as other system details like processor load, voltages, and more. Some of them can also automatically or manually adjust the speed of your laptop's fan for best performance. Here are a couple that I've used before:

SpeedFan: In addition to monitoring fan speeds, voltage, and processor temperatures using your laptop's internal sensors, SpeedFan can also access S.M.A.R.T. info to determine your hard disk's temperatures. The small application offers fan control, charting, and easy-to-understand graphics (like a flame next to each processor core that is over the recommended 50 degree Celsius mark). Windows PCs.
Real Temp: Real Temp is designed specifically to monitor temperature for all Intel single, dual, and quad core processors. In addition to showing the temperature and load of the processor, it also shows the CPU's "TjMax" or safe maximum operating temperature and how far from this maximum temp your processor is running at. Another interesting feature of Real Temp is its tracking of your highest and lowest temperatures since you opened the program. Unlike SpeedFan, however, Real Temp doesn't allow control of fan speeds. Windows PCs.

For Macs, there is a free Temerature Monitor application that's also available as a dashboard widget. Linux users can read the CPU temperature from a shell prompt.

source from about.com