To be honest, I wouldn't mess with mother nature. Just a personal choice. Weather is weather, and there could be serious repercussions for messing with it, and if enough power were gathered to stop a drought, chances are it would swing in the exact opposite way, thus causing torrents of rain.
Tools:
Bowl of Water (Not from the sink. Perferably Rain Water gathered earlier, or specially-made ritual water)
Chalk
Towel (If done inside, several towels)
A Cloudy Day (You have to have rain to Call, ya know!)
First off, draw yor circle on the ground. I know, I might be the only one who does this in the entire magickal world, but that's what I do. You can ignore this step and go onto the next one.
Second, take the bowl of water and move it around in the bowl. Allow your mind and spirit to contemplate it, and meditate on it's power. How it is so powerful, yet is required for the very survival of everything on the planet. Think of how plentiful it is, and how gently it flows in the bowl. Picture, in your mind, this motion forming in the clouds.
Once you have reached a state where you believe you can call the rain from the heavens, and pour down upon the earth, recite the following:
Oh Water that Flows from the Heavens,
Oh Water that falls from the sky-
Pour down your might upon my brow,
so that ye servants shaln't die!
Bring forth the life that pours from the darkness,
Bring them forth from the clouded sky-
So all may gaze in awe and wonder,
As ye Might gushes forth from on high!
Fall rains! Blow winds!
Pour upon my head!
Ye blessed tears fal down upon us,
Lest the Earth shall die!
I call forth the Water from Heaven!
I call forth the Tears of the Gods!
I call forth the Life in the Darkness!
I call forth the Might on High!
So Mote It be!!!
Upon the final line, as you recite So Mote It Be pan-toss the water straight over your head, attempting to make it fall like rain upon your head. Look up toward it, and allow it to rain down upon your face.
Confirmations: I have had several instances of Comformation that the spell worked. One instance, I was doing it, and I was met by a gust of heavy wind from my back... Even though there was a treeline to my back. Thunder may be an indicator, aswell as lightning. But if it Lightnings, I reccommend that you run away. See the Recitement tips toward the bottom.
(Reciting tips: Recite as if you are desperate, and pleading the clouds to pour upon you. As if your life depended on it. Try to build up to the last lines, aswell. If you can somehow make yourself cry, it would SERIOUSLY help the spell.
I know I don't have to tell you guys this, but BELIEVE the words will work.
Oh, and don't cast it in a rage, stress, or anger... :/ I kinda dropped the ball one day and made a storm out of a couple of small clouds to rain out my lil bro's baseball game becouse I didn't want to take him to it- And I regretted it so much I went and helped them unflood the fields by hand.)