do i need a bike cover?

[twinkiex]

I tried to search for this answer honest. I am storing the bike in my back yard locked up to a post. I have been covering it with a tarp. I was planning to buy a nice bike cover, but is this necessary? Will water hurt the bike?
Still in the break-in period having more fun than I thought possible.

 

[azbill]

rain shouldn't hurt it
most important is to keep magneto dry
(it's behind the cover beside the clutch lever cover)
not sure about tucson, but the monsoons seem to be done here
I would be more worried about sun damage than water myself