The Collaborative International Dictionary of English v.0.48:

Fair-weather \Fair"-weath`er\, a.
   1. Made or done in pleasant weather, or in circumstances
      involving but little exposure or sacrifice; as, a
      fair-weather voyage. --Pope.
      [1913 Webster]

   2. Appearing only when times or circumstances are prosperous;
      as, a fair-weather friend.
      [1913 Webster]

   Fair-weather sailor, a make-believe or inexperienced
      sailor; -- the nautical equivalent of carpet knight.
      [1913 Webster]