KenDuncan

I think your trees should be fine.
The North Carolina Arboretum keeps some of there collection in a walkin cooler all winter until there is not a threat of frost. Great idea if you can do it.
Bill Valavanis in Rochester New York keeps his trees in his garage with a heater set on 27 degrees F., so they stay frozen all winter.
Here in South Carolina all I can do is leave them outside on the ground all winter with the freezing and warming up, that is not so good but they have survived for over 30 years with these conditions. We have had temps. from 24 degrees F to 75 degrees F. this winter.
I have had some damage in past years to azaleas and some other tinder plants when we have had temps. in the teens and single digets.
In the spring after the new growth comes out and we have a late frost, that seems to do the most damage.

Ken