I got a request from a reader about winter damage from trees. This is the information I found:
Frost cracks are not actually caused by frost, but by fluctuating temperatures. The cracks are most often found on the south or southwest sides of trees, which get the most direct sunlight. On a cold, sunny day, the sun warms the bark and wood of the tree, causing them to expand. At night when the temperature drops rapidly, the bark cools faster than the wood beneath, forcing the bark to split vertically as it shrinks over the expanded wood. This is most likely to occur on trees with wounds that have already weakened the bark, especially if they are young trees or trees with thin bark. These cracks are rarely fatal to the tree and can be minimized.
Examine the crack in the tree bark. If the sides of the split are smooth and the bark is still firmly attached to the tree, do not do anything. The tree will eventually form a callous over the crack.
Remove any bark that has separated from the wood of the tree. The bark will not reattach if left on, but will prevent the tree from callousing properly. Cut the separated bark from the tree with a sharp knife. Make sure you do not cut into the tree wood, but only through the bark layer.
Shape the wound while you cut to resemble a skinny, sideways football with the pointed ends at the top and bottom of the wound. This shape will make it easier for water to drain from the bottom of the wound rather than collecting on the bark.
Check the frost crack periodically in the spring and summer to make sure no organisms are invading the tree through the open wound.
Thanks to http://homeguides.sfgate.com/fix-frost-crack-tree-74301.html for this information.