Let it Rain
THERE ARE SEVERAL WAYS to approach animating rain, probably because rain falls in several ways depending on wind conditions. I chose an average style of falling rain that can easily be expanded upon based on your own needs.
Rain, to our advantage as animators, is repetitive. Reusing assets is one of the strengths of Flash. You only need to animate one raindrop and then populate your scene with multiple instances of it. You can then control how your rain acts by adjusting the angle at which it falls, its speed and how many instances of it appear at any given time.
1 Use the Brush tool to draw your rain drop. Gravity suggests that ...