Does Dust Affect Cooling?

[Mackass]

My computers almost a year old, and it's currently quite dusty inside. Recently, my CPU temperatures have reached an astonishing 45*C at certain times, where as a year ago, when everything was new, my CPU only ever reached temperatures of around 38*C maximum. I know there's been a heat wave recently, however this was roughly the same last year, so I was wondering, will cleaning out the PC give me any substantial improvements in temperature readings? Also, my AMD CPU fan, will taking it out and clearing the dust interfere with the layer of thermal paste?

 

[Mackass]

Does the compressed air reach the dust in those hard to reach places, like really further in? And is it okay to spray it on other places, like the motherboard and graphics card etc without causing any damage?

 

[Mackass]

Cheers, I'll give it a go.