First of all: never switch off the power if you didn't switch the box off via the menu. This can really damage the box. If there are regular power outages at your place, please use an UPS (and this applies to all your electronic equipment; for that reason I use 3 UPSses here.
If the power has been switched off, leave it of for at least a minute; that is to discharge all capacitors, and has nothing to do with the temperature.