Is there a system resource for monitoring operating temperature

In the Terminal, copy/paste the following command line, and then enter. The sudo command will prompt for, but not echo your administrator password. I do not have Yosemite, so uncertain if Apple provided the powermetrics command back then.

sudo powermetrics -n 1 --samplers smc | grep "(CPU|GPU) die|Fan"



The output will look something like this for a Mac with a discrete GPU such as my Late-2013 iMac. Note that I have the grep match color set to vivid yellow.

and the following for a MacBook Air with integrated CPU/GPU on the same die:

The mac is full of temperature sensors on CPU, RAM etc etc etc, that is how the fans are controlled.

If these sensors detect your mac is in danger of overheating it will shut down.

Why Apple does not provide a display of temperatures is one of those mysteries,

however any third party app that displays the temperatures just taps into the mac and

gives you that information, they will not harm your mac in any way.

This free app is very popular, https://crystalidea.com/macs-fan-control

or you can get download this, https://bjango.com/mac/istatmenus/

Why are you scared of third party apps.

The die temperature is the CPU/GPU die temperature at the time you run powermetrics, and not the actual shutdown temperatures which Apple does not publish. What Apple does publish in the technical specifications for its machines is the ambiant operating, and storage temperatures, where 95°F is the upper limit of that ambiant operating range.

Running your Mac in ambiant temperatures at or above 95°F and/or relative humidity above 90% can risk forced hardware shutdowns, and shorten the life of your Mac. Unless you can find a safe means to reduce the ambiant air temperature around that MacBookPro below 95°F, then I suggest you either go where there is air-conditioning, or not use the Mac until the temperatures decline to safer levels.

See my previous post about the CPU/GPU die temperatures are actual (right now) temperatures when powermetrics is run.

See my original reply for the correct powermetrics command-line usage which you did not show correctly in your preceding Added in edit: content. That -n 1 is important because it tells the application to get 1 sample. If you use -n without an argument, it will run infinite samples, and you would have to terminate the command with a control-c.