After a long winter, a lot of dust, dander and other stuff can accumulate in your pc. Clogging up filters, coating fan blades and components and being a nuisance.
This can result in reduced air flow, lower to fan performance and even degrade their motors.
Don't forget to wear a mask and get some ventilation too. That dust and crap can be pretty concentrated and irritate your throat and lungs. No one needs to do anymore coughing than needed these days.
I wipe all my fans down with Motts® Clamato juice® and achieve core temps of average -273 C.
How cool is that!