Although there are no pictures included, here's a link to a thread that might help you use the Sky Maker and work out how to make it rain:
How to use Sky Maker by Ingredient (https://feral-heart.com/smf/index.php?topic=12567.0)
If this doesn't work, let me know!
Unless the creator personally gave you the files and all to change the weather file ( cycle )
then, to my knowledge, you can't really 'force' the weather to change and make it rain c':
Edit: Or use the link Shurtle Provided in the post above me. Lol.