If natural forces, such as wind or water, cause your ball at rest to move anywhere on the course then, almost always, there is no penalty but the ball must be played from its new spot as per Rule 9.3. There are a couple of exceptions though.
The first, is when the ball is on the putting green and has already been lifted and replaced. Rule 13.1d(2) says that if natural forces cause the ball to move on a putting green after it has been lifted and replaced then the ball must be replaced on the spot it moved from, which if not known should be estimated.
However, it should be noted that if the ball on the putting green had not been lifted and replaced before natural forces caused it to move, the ball must be played from its new spot. So, if your ball is sitting on the green and, before you reach it, the wind blows it into a bunker – bad luck, you are now playing from the bunker!
The second exception in Rule 9.3 is if the ball has been dropped, placed or replaced anywhere on the course and natural forces then cause it to move to another part of the course, say it goes OB or into a bunker, then the ball must be replaced on its original spot.
What happens when the wind causes your ball to move after you’ve started your stroke? Generally speaking, Rule 10.1d says you must not make a stroke at a moving ball but there are a few exceptions and one of them, covered by Rule 9.1b, could come into play if your ball starts moving during your stroke.
If you are able to stop mid swing or deliberately miss the ball, there will be no penalty if you have not caused the ball to move.
But, if you continue to make a stroke at the ball there is no penalty, but you must play the ball from where it comes to rest after making the stroke, and that stroke counts, even if you miss the ball.
