Psensors is a GTK-based program which lets you view a graph of your computers fan and temperature sensors. It's the best there is for this purpose since it's the only program that does this.
What it looks like
Here's an exmaple of Psensors in action. As you can see the CPU temperature graph plotted in green goes up and stays up when a Linux kernel compile is started.
Psensor pulls the data it graphs from the sensors command from the lm_sensors package. Thus; you will need to have the sensors module (it87 or similar) loaded and working in order to get any useful data from it.
You can't have it on Fedora
You will need to download and compile it yourself if you are using Fedora, RHEL or CentOS. It's not included in their package repository. The good news is that compiling it is strait-forward with the usual ./configure && make && make install procedure.