How to check the CPU temperature in real time without using any software!

As far as I know, most system units have an exhaust fan. I have one too. You can install a separate intake fan (I don't have one). And everything is fine; neither the CPU nor the system gets hot, and as for dust, that's a given. I didn't think about it before (the computer wasn't used for long at that time), and as a result, the CPU heatsink got clogged with dust (Pentium 4), and my computer started shutting down periodically due to critical overheating – 110 degrees. P.S. How can exhaust be useless? It's located at the top of the system unit, where hot air accumulates (simple child's physics), and therefore this air is blown out of the system unit.