My Omnium was stored outside for the first 3 years, under a roof but otherwise exposed. It rains a fair bit in Denmark so it did get surface corrosion on a few bit but I wouldn't say it's wrecked. Just be on top of the maintenance and don't forget the grease where required.
This, a car port type cover where its protected from above and at least on a few sides from most of the direct rainfall is best. As soon as it stops raining it starts drying out. Car/mc/bike covers are death, keeps all the water in a nice infinite humidity bag.
My Omnium was stored outside for the first 3 years, under a roof but otherwise exposed. It rains a fair bit in Denmark so it did get surface corrosion on a few bit but I wouldn't say it's wrecked. Just be on top of the maintenance and don't forget the grease where required.