The problem occurs when the tree or shrub hasn’t stored enough water to last through winter. This will result in the tree drying out. It can dry out so much that it drops its leaves or in the worst case scenario it even dies. To prevent this from happening, keep watering your trees and shrubs right up until the ground freezes. That way, they can absorb enough water to last all winter.
Another option is an antidessicant. To give your evergreens even more protection, you can spray them with an antidessicant. This gives the trees a waxy coating that covers the pores on the leaves and thereby sealing in the moisture. Two applications should be all that is necessary. I suggest one application in late fall and another in early February. This should provide enough protection for your plants so that the drying winds from winter won't even faze your trees.