Check out this if you ever need it for the future: How To: Add Weather Effect With Overlay
An example:
EXT. BACKGROUND - DAY with effect HARD RAIN
NARR
Bla bla bla, whole scene goes here.
EXT. BACKGROUND - DAY
NARR
Scene goes here where it’s not raining anymore.
(So, basically, to turn off a weather effect, you will need to re-write your background without the effect on it, and re-place all of your characters into the scene).
More (similar) detail here: