Hello Linux Enthusiasts.
lm-sensors is a nice tool for monitoring the CPU temperature.
To install lm-sensors, open a terminal and type:
$ sudo apt-get install lm-sensors
To use it, type in your terminal:
$ sudo sensors-detect
You will be asked if you want what it finds to be added to /etc/modules so that it will be loaded with the other kernel modules. Type yes for doing it.
Now, when typing sensors in the terminal, you will get the CPU temperature:
This is it. Enjoy.