As long as you don't have a vapor barrier sandwich inside the wall somewhere, frost on the outside of the envelope is not a bad thing. In winter, it is better to have outdoor air finding its way in, as cold outdoor air has less moisture in it.
Somewhere inside the wall, there will be a plane where it is at freezing temperature. Whenever possible, this plane should be inside of free air or space occupied by insulating material. Any moisture that freezes at that plane should have a path in or out when winter is over. Since you have exterior clapboards or lap siding, they should be able to breathe enough to let the vapor out once it warms up.
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