Chinajohn:I cannot see how it would be possible, AFAIK what we see 'in game' is actually still HD photographs moving scenery would require motion clips.
Actually anything IS possible John. Flash runs using layers so moving clouds or rain even could be added to a layer which overlays the photograph in the background. Layers is how the avatar swing, ball flight, etc. is added to the screen.
RainEffectonStAndysandgeese.swf
But like everything else added to the game there is a price to pay. As ScottHope noted above it would add to the meter problems. Unless the rain/cloud movement/etc. was shut off during a swing much like the grid and dots can be removed during a putter swing.
WGT would weigh the cost to add such a feature against an estimate of how many additional members it would attract plus any increase in usage of current members. Would the added realism prevent members from leaving? It all boils down to ROI with WGT.