Fan Noise in Hot Weather

Your computer looks very clean. There doesn't appear to be any dust. But if there is dust, then I suggest that you blow it out with compressed air. Or, go to your local department store or sporting goods store and get a pump that is used for inflating a mattress. These pumps are excellent for blowing the dust out of a computer. I wouldn't worry about blowing dust into something critical. If you direct the airflow away from the power supply, you shouldn't have any problem. And if you don't touch anything, you won't do any damage to anything.

Also check the direction of the fan airflow and for any obstructions in any case vents. You want to have clear vents with clean filters (if applicable) for intake and the fans should exhaust heat out from the case. Also, fans are cheap. I know you said they are hard to access but you might want to swap them out for high efficiency airflow fans and maybe even consider adding an additional unit if you have the space.