There is no guaranty that your palm trees will survive a harsh winter and what we have seen in the past few years that it may be best to protect them each winter. Here's is my recommendation and what I am personally doing to protect my 20 plus palm trees.
Step 1: Wrap them in heat cable.
In this photo I used C9 Christmas lights, but the heat cable would be better.
Step 2: Covering the trunk
From the bottom of the tree place roll insulation around the trunk, overlapping a bit as you go up the tree. Go all the way up to the fronds.
Step 3: Stretch Wrap
Do the same with the stretch wrap to protect the insulation from water.
The heat cable, insulation and wrap can be found at Lowes or Home Depot. I found the best pricing for the heat cable was on Amazon.