After watching some spiderman type guy scale the side of our 4 floor apartment building once (to get to his friend on the top floor), I informed my wife that I would never store my bike on the balcony. That being said, it's not all that bad as far as weather if you know it won't get wet and you can lock it to your rail. I still wouldn't do it with anything but a beater, though.
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It's like riding a bicycle