Q Now that it has got warmer, I am concerned that our Mac Pro and iMac computers could be getting too hot for comfort, particularly in the late afternoon when some sit in full sunshine. Can I use a normal indoor thermometer to monitor them, or is there something better?

A No computer, even when shut down, should be left in sunshine, as it can cause significant light and thermal damage to cases, connectors, cables, and in the extreme even internal components. Sometimes it is actually preferably for the computer to be running, as its cooling fans will then be spinning, and it will be using them to control its thermal state.

If you cannot move your Mac Pro systems into well-ventilated shade, at least draw blinds and minimise the light falling on them and subsequent solar radiant heating.

Normal indoor thermometers will tell you the temperature of the cooling air that they draw from ambient, but not the temperature of critical internal components such as processors and hard drives. To observe conditions inside a Mac, install Marcel Bresink’s System Monitor (Mac App Store, £3.99), which puts CPU temperature and fan speeds into the menu bar, or possibly the more limited Temperature Gauge (Mac App Store, £3.99).

Updated from the original, which was first published in MacUser volume 27 issue 9, 2011.