Answer: This rhododendron needs a winter chilling period so it would not do well as a houseplant. (Please check with your veterinarian as to toxicity for your cat; a cat can certainly do damage to a young rhodie, breaking the branches by climbing it and so on.)
You might be able to overwinter it in a bright cool room at about 35 to 40 degrees. Keep the soil just barely damp while it is resting and do not fertilize it. This might be the least risky path.
Your zip code places you in zone 3, but this rhododendron is only considered winter hardy to zone 4. For this reason I do not think it would be winter hardy outdoors, even if it had been planted sooner with more time to become rooted and established.
At this point you could try planting it in a very sheltered location. Mulch deeply in late fall once the ground has turned cold, apply an antitranspirant spray per the label instructions, and provide it with a windbreak this winter and hope for the best. But sadly I do not think it would make it. I wish I could be more encouraging.
Good luck with your rhododendron!
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