Outer bark can shed from a tree without it losing the living inner bark. If it is the inner bark that is being lost the tree can't survive and will quickly turn brown. So if you tree is still green and relatively healthy looking I suspect that the bark loss is not a concern but as you indicated may be related to the extended drought you all have been experiencing. During drought it is best to provide a wide are beneath the branch spread a good deep soaking once a week or so if possible.
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