I know it sounds a bit 'soft', but I used to have a large, biggest I could find, golf umbrella attached to the back of the cages, so that when I was out tending to them in the rain they still remained dry when the cover was off (and I was too!) If it was light drizzle the Umbrella would suffice as their shelter to keep them dry, if it was really awful weather then i had some clear thick plastic (bought off the roll to the size required from a hardware store/Band Q place). It was attached to the back of the cage with a staple gun and could be rolled overthe top and the front when required. Attached to the front end of the sheeting was a wodden piece of pole, this helped with the rolling up of the plastic and added weight so the front didn't get blown off the cage. I am lucky enough nowadays to have a fantastic windowed shed that they all live in !