Making rain:
In the "In the Storm" theme, I made a brand new layer on top of all the other layers, filled it with white, and set it to "Multiply," which basically made a completely invisible layer.
Then I added noise to that layer (Max intensity, no color saturation, moderate coverage), which put little black dots all over. I used the zoom function to make the dots bigger, then motion blur to streak the dots.
Then, for good measure, I duplicated that layer, and zoomed it back out a bit, so there'd be more sizes of raindrops.
If I were to try again, I'd zoom in a bit, streak it, and THEN zoom in a bit more in the duplicate layer, to eliminate the conspicuous edge where the pattern repeats.
