Quite possibly. Either bring them in the house or shelter them in some way, like covering them with blankets or plastic at night like I do to extend my tomatoes.

I guess I need to reword my question.
The canna tubers are frozen from the thirty degree temps we have . Will they go to mush?
Does the ground freeze in zone 8 in the winter?

The ground never freezes here like it does in PA. On the coldest day we ever have the ground is still workable. Down here, we don't even dig them up or mulch. You might be able to rescue some. It's hard to say. I would spread them out somewhere, the basement, the attic, under the bed, any place at all, on a plastic sheet to protect the carpet and see if they get mushy when they defrost. Cut off the mush and hope for the best. If you don't cut off the mush, it will spread.

Thank you folks.
The cannas were mush and ended up in the compost. I had some that were still in the ground and they are fine.
Our freeze came really late this year. Usually the canna tops die off way before now and I dig them and leave them to dry.
This was my second year growing them, so I have learned something about them.