If that was your first spell you've ever casted, then there are a few reasons why your spell may not have worked.
Practice, practice, practice! You are probably just inexperienced. You don't just do something once and expect it to work the very first time, practice...
Have you looked into the basics yet? A lot of times knowing your basics is a very important thing when starting with your practices. With weather spells, you need a strong will and mind power, much like when working with elemental magick and any other, for that matter. This can be achieved by meditation, visualization, cleansing your aura and energy. When I first started casting, I was totally oblivious to this very important factor and all my spells usually failed. I was very frustrated and ready to give up on everything. Then, I came on this site and researched why I might have failed, the answer then came clear to me. Thus, I've decided to start all over from the very beginning to step one of everything: meditation. Good luck, and don't ever give up :)