In most cases, our in-wall and in-ceiling speakers can weather the elements perfectly well. Speakers will work fine in overhangs, wrap-around/covered porches, garages, and more.
Anything you put into the care of Mother Nature, however, will be unavoidably affected in one way or another. There will be some discoloration over time, but it's nothing a fresh layer of paint can't cure.
Damage will mostly affect the color and the housing, but the inner workings should not fail, since the great majority of speakers are made of synthetic materials. Locations with marine air will certainly accelerate the discoloration.
