theres many factors to consider in the success of magic. for starters you have to believe fully that it will work or it wont. the moon phase also affects the success. but mainly if you believe and it does not conflict with universal will and law it should work. if you believe it will work i will tell you an easy rain spell on this site. just clarifing its not my spell but it is as follows:
"ancient gods and goddesses i invoke thee waters from the sky
let it be i command thee now to thee all listen to my desire
chant this 3, 5, 7, or 9 times higher the number the more potent the result.