Question
I have a potted Norfolk pine tree that I move outdoors, to the deck, for the summer season.  The tree has grown a lot this summer and is almost 8 ft high now.  I live in Ellisville, MS which is southern Mississippi, about 100 miles north of the coast.  Would the tree survive winter temperatures if left outside?

Answer
The problem may come in the pot freezing and killing the roots. The tree will grow and survive in the ground since that far south the ground will not freeze normally. This is too large a tree species to have in a pot. I would think about transplanting it to the yard.
make sire if you do you dig the new hole twice the size of the pot and as deep and fill with good top soil. Mulch around the tree with not more than 3 inches deep of organic mulch not piled up on the trunk. This will help hold moisture and protect the roots from the cold. IF you leave it in the pot be prepared to protect the pot from freezing maybe with a blanket around the pot with a light bulb under the blanket to make heat. Do not forget to water it as usual during the winter months. l