I just picked up an wood canvas Old Town OCTA that has been outside the last 3 summers. It was up side down, up on horses. The rain would run down the hull to the gunnels which had a decent coat of paint on their undersides, then run down the gunnels to the bow and stern. The water curled around the gunnels and somehow rotted the end of one stem. One gunnel also shows sign of being a little bit punky, especially around the end.
I would avoid leaving the canoe outside if at all possible, sounds like a small canoe cart would be a good option, then you could even avoid lifting the canoe over your shoulders.