I recently moved in to an apartment with out air conditioning. This is fine most of the time as I am in upstate New York. It only ever gets above the high 70s during the hottest of the summer months. And when it does, I'm stubborn enough that I'll just deal with wearing minimal clothing around the house.

However, I'm worried about my computers. I'm a software developer and gamer, so many of my machines are very high powered. And at least one of them is a server that must be left on 24/7 (not just a game server - also serves multiple websites). I've never before had to worry about the heat too much, as I always lived in buildings with central air. The in building temperature rarely got much above 70 F. All of the machines I built had good enough air cooling that I never saw a problem.

Now the temperature in building is pushing 100F and I'm worried that the machines will not be able to keep themselves cool enough by simply blowing already hot air over themselves. The hottest of them I've turned off. However, the server I cannot. It's an old Dell (not custom build) that runs on a Pentium 4 (2.2GHz). It only has a single hard drive, integrated video. And it'd not running any processor intensive servers. Just basic LAMP. It used to run a MUD server, but that's off for now. So it should be idling most of the time.

I haven't been able to find any sort of built in temperature sensors in the hardware... at least not any that the programs I've found in the Debian repository can read. And it's an inherited machine to which I do not have the full specs, so I don't know the tolerances anyway. How worried should I be about it melting down on me? How worried should I be about the hard drive melting or becoming corrupted?

To generalize the question for other people, what are the safe temperature tolerances for most machines. How widely does it vary, and how does one go about determining when their machine is running too hot and needs to be shut down?