It is probably too cold for your zone. If you really want to know, you can trim tip, and see whether the inner is moistly white. Somebodys trim upto 1/3 in the spring before new leaves grow; I don't do it every year, and not dart to trim that much, only tips, just to be safe.

I suggest that if it is too cold you might try putting it out in the morning and bringing it back in for the night, at least until things warm up. Jerry