It can happen with dogs so, although I haven't seen a cat do this, would suspect there are the rare cat that also does it. Or it could be seasonal alopecia where they get a skin condition and hair loss with matting which is often in spring or summer.
Whatever the cause, for the health and welfare of the cat, it should be combed daily to stop matting which in itself can be painful. The matts pull on the skin, and sores can develop with lack of air circulation and dirt getting trapped.
If it is feral then it's welfare should be considered and decision made whether it is fair to let it go through this every year
