Keeping your computer desktop clean as well as cleaning out the actual machine is very important. The picture to the left shows an extreme example. But if the internals of the computer are dirty then the performance of the computer may be affected as well as shortening the life of the components such as the CPU and the GPU. Dust such as this that covers fans and heatsinks is a perfect way to end the operational life of your computer sooner than later. That is why compressed air cans are such a good idea; the short blasts of compressed gas are perfect for getting rid of the tenacious dust and lint that gets stuck in the components. This makes a computer much happier if it is clean and running cooler. I just wish you could buy a cheap desktop air compressor for cleaning out your computer. That would be very useful. Keeping your computer room cooler is another good idea in summer.
Speaking of desktop vacuum cleaners, this desktop vacumm cleaner would be very good for getting rid of dust: Amazon link. Perfect for small jobs. There are small compressors for pumping up car tyres that are 12 volt powered. I wish you could get those in 240 volt ratings for inside desktop use. Purchasing one of those would be better than buying the compressed air cans all the time. That would add up. You can use the Linux command line if you wish to monitor your CPU temperature.
Type this command to install the sensors package.
sudo apt-get install lm-sensors
Then run this command to start detecting the available sensors in your machine.
eren-titan ~ # sensors-detect
Answer YES for every option that you want. After all of that you should be able to monitor your CPU temperature and any other options that are available.
eren-titan ~ # sensors coretemp-isa-0000 Adapter: ISA adapter Core 0: +43.0°C (high = +80.0°C, crit = +90.0°C) Core 2: +43.0°C (high = +80.0°C, crit = +90.0°C)
Read more about this process here: http://askubuntu.com/questions/53762/how-to-use-to-use-lm-sensors.