In the current hot weather I would avoid covering a hutch with anything other than mesh fly screen material.
Even overnight.
All if takes is one small accident where you sleep in or rush off to work and forget the cover is on, and your piggies will overheat very quickly.
Even the covers that have a ventilation panel in them (usually just strip near the top) will not offer enough air flow in the warm weather.
It's the equivalent to leaving a dog or a child in a hot car with the window cracked open - very dangerous indeed and usually fatal.
If you are concerned about predators, then consider using a wide webbing strip around the entire hutch (the type usually used to secure loads on trucks).