If the car was on the road, it would be in the elements, so if dry storage or the carcoon (as the lads mentioned) isnt an option, I would be doing my best to shelter it, without the shelter potentially damaging the car - for example, if you had a space you could cover to keep the majority of the element away from the car; boundary wall and side of house, bridge the gap with something suitable.
I had wedding ribbon on my car once, and only for about 3hrs and of that, 25 mins driving; the bonnet, was nicely marked afterwards - cant imagine what 3 months under a cover would do.....granted, thats my view of damage; many others wouldnt even bat an eyelid to it.