To show hardware temperature on ubuntu you can use program called 'psensor', this cool program allows you to see CPU cores temperature, CPU usage, GPU temperature, etc, in a nice graphical interface.
Psensor is a nice tool for monitoring hardware temperature on your computer, 'psensor' is part of ubuntu repository, so you can install 'psensor' on ubuntu like this:
Once installed you can open 'psensor' from ubuntu dash by searching with keyword 'psensor'. It should be look like this:
You can change the background and the sensor graph color with any color your like, see this:
Pretty cool, huh?