I installed these over two of my vents and they worked great.
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
I can open the vents almost all the way... not completely open but far enough that they still work fine and no worries of rain getting in or hail/ storm damage to the vent cover itself.
Now if I could just find something to protect the shower skylight......