Little Hawk, its a natural occurence here on the west coast with western red cedar. Its called "flagging" and is a response by the tree, most summers, to low rainfall, as kat noted. It is not something to be concerned about in western red cedar and does no harm to the trees.

I would assume that it would be the same with eastern cedar species. Check out other cedars, in the area, to see if its occuring with them too. Cedars are wonderfully messy trees and contribute to a lot of the detritus in my house, that the dogs bring in tangled in their fur. Gnawing and pulling it out keeps them busy for hours.