Managing your PC's temperature is always important, but it gets really crucial during summer. As the weather gets hotter everyday, you want to make sure your computer stays in the best possible working conditions, either in the office or at home.
First, place your PC is in a well ventilated spot, not too close to the wall and away from heating sources or direct sun light. If you work with a laptop, always use it on a desk or at least put it on some kind of rigid support like a board or a hard-cover book, so that the ventilation holes, usually located at the bottom of laptops, allow air circulation.
Second, try to keep room temperature to a reasonable level. It will be good both for you and your computer. Turn air conditioning on or use a fan, whatever suits your budget. Having an average temperature of 25ºC should be enough.
Last but not least, use a software application to control the temperature of CPU, hard drive, motherboard and other core elements in your PC. You'll find a wide selection in Softonic to choose from, but if you're not sure about which one is the most suitable for you, take a look at this post written by Nick a while ago, where he gives some more advice on controlling your PC temperature.
In any case, take whatever measures are necessary to avoid the scene depicted in the accompanying image. Yes, that's my PC. Last summer it got so hot I had to open it and use my home fan to cool it down!