Yes, because mold is actually a fungus. If spores are present and humidity is too high, the oscillating fan might not move enough of the humidity away from the interior of the plant. Inside where I can control it, I like to be 50% or under humidity when the buds begin to swell up. However, if you keep the air moving and the humidity in check, you'll probably never see it. This is why tents work best inside.
I know at least for now your choices are garage or shed. You'll have to be on top of things if your in a cold weather climate. If you're ever able to bring it inside, please do ... it will be far less work for you.