I installed a free software called SpeedFan. It’s telling me that my laptop computer is reaching internal temperatures of 70 degrees Celsius.
Is this even remotely possible? That’s not far from water-boiling temperature. I’m not playing games or anything on this laptop. How is it not melting? Is this software wildly inaccurate? (I recently installed an app on my smartphone that told me that my smartphone was 150-170 degrees Fahrenheit, and I’m quite skeptical about that, too.)
70 is quite a long way from boiling, and a perfectly plausible temperature for the cpu core in a laptop. Graphics cards often run around 85 under load.
It’s perfectly reasonable, if a bit on the high side.
It’s measuring the temperature on the silicon die itself. The laws of thermal conductivity guarantee that the temperatures will rise as you approach the heat source. So, the internal case temperature might be 45 C, the heatsink 60 C, the heatspreader 65 C and the die 70 C.
Silicon has little problem operating at 95 C or so, and under heavy load may reach that. It starts to lose lifetime around that point, but not obscenely so.
Thanks for the feedback. Makes me worry less.
I’d envisioned the inside of a computer being somewhere only a bit warmer than human body temperature; maybe 45 Celsius at the most. Shows how much of a computer techie I am NOT. 
Since I’ve used this laptop for nearly 6 years now - probably longer than I should - what is the average, normal, healthy temperature for a laptop?
Sounds about right. A few years back I had a MacBook that would get extremely hot - to the point I had to get a 3rd party application (SMC Fan Control) to make the internal fans work correctly:
http://www.macinfo.us/how-to-prevent-your-macbook-from-overheating.php
Get a top-end video card, run a game benchmark at high res for an hour or so, and then grab the card’s heatsink. Tell me if you think it’s body temperature (once you finish treating your second-degree burns) :).
Just as another data point:
I run an app called Core Temp on my laptop (which I use as a “desktop” because it’s always running and hooked up to a mouse, external keyboard, and large external monitor).
I’m sometimes (about 5-15% of the time) running in the 70 to 77 degrees Celsius range, but most of the time it’s around 45 to 55 Celsius.
Most CPUs have spec’d max temps around 68-72 deg Celsius.
That doesn’t mean it’ll break if it’s hotter than that. It means that they tested it up to that temp, and if it’s hotter, they won’t claim that it will run as it’s supposed to. There’s often a good bit of safety margin.
Above 90 or so and you might be risking damage.
One thing to do is get some canned air and blow it at your computer with the case off (do this outside). Caked-on dust is a good thermal insulator.This can be trickier with laptops, but still somewhat doable.