Definitely a big no to any kind of waterproof tarp style protection. Waterproof tarps also tend to be stiff and if the wind picks up the tarp will flap and abrade the paint.
Most quality car covers are definitely not water proof and most are only mildly water resistant. With the various car covers that I have used, a good rain storm will wash significant dust on the outside of the cover right through the cover leaving me with a dirty car underneath the cover. My 142 has been living outside for nearly 10 years since finishing restoration and moisture / rusting due to the car cover is a non issue.
The primary functions of the car cover are
- dust reduction (as long as the cover stays dry)
- reducing / eliminating sun damage
- protection from bird droppings
- varying degrees of scratch / ding protection depending on the material used. This can be useful if you are continually having to walk past the car in a tight spot.
So, assess what your exposure to the elements are. If you get a lot of rain which will wash dust through the cover and necessitate washing the car anyway and you don't have direct sun exposure then a car cover may not have a lot of upside.
If you do go for a car cover do not go for one of the low cost 'fits a bunch of cars' option. They tend to be loose fitting and if you are subject to significant winds they will flap in the wind, potentially abrading the paint and may become air borne if not secured with a belly retainer under the car. Custom fit covers reduce the flap; but, cost more and take longer to arrive because the are cut to order. When you get to the custom fit cover level, you might want to consider the 'garage in a box option'
https://www.canadiantire.ca/en/pdp/s...3.html?loc=plp