NOTE: It can be dangerous to try to control the weather. However, at certain times such spells are necessary. Remember that Mother Nature is a powerful force. It is not easily that she can be persuaded to change her mind.
Burn together out of doors in a wild, lone place... heather, fern and broom. As the smoke rises up visualize it forming into clouds, and these clouds turning black, and finally belching forth their store of rain to the ground.