Rain. An essential to life, loved by the wild and farmers, dreaded by those with no conscious connection to the real world, like urbanites. Soft, good rain paced out so as to feed but not harm with droughts or floods. How does one guarantee such a emotive elemental, which takes it's form around harder stuff yet will always, given patience, wear it down to fine grains?
Let's look at rainforests, the ancient rainmaker. We have long known that rainforests cause their own rain, sustaining themselves and areas around them. They soften and cool the weather by changing the atmosphere in a huge group effort of plants shading, breathing in greenhouse gases and out fresh oxygen, and pinning down dust with humus, moisture and root stock. It is a natural air conditioner, which you can feel and smell as soon as you step inside of one. And the smell is an important clue for rain making. Recent scientific discoveries have shown how, or part of how a rainforest creates the rain, besides cooling the atmosphere. It seeds clouds, naturally. Micro organisms are created in the rainforest and released into the atmosphere, creating a catalyst for the moisture in the cooling air to form around. These micro organisms are aerobacter. One way for us in humanity to create rain using a natural method is to imitate the rainforests. We already, when desperate, seed clouds for rain. If we cultivated the benign aerobacters of the rainforests in an industrial way, and then released them into the air (taking winds into account) around lakes, reservoirs, rivers, dams, farms and wilderness we could get the rain where it is needed. The best time to do it is as the air cools in the evening, when moisture from oceans or other humidifying sources is strong. Cooling the air with forests is a good long term plan. If you are "seeding" for an area where desert has spread or erosion is likely, smaller amounts would be wise, until there is enough plant life to hold the moisture and prevent the damage of element upon element with little Living things as a buffering variable.
In all things natural, it is unwise to take and not give back. Besides the law of karma, it is a way to guarantee long term abundance all round and can even feel good. Elementals are known for their cantankerous dislike for greedy, stupid people, and love of plants and animals in their free state. If they do not get some wild place to reside, they can be dangerous and destructive. Or you can ignore the warning, and just take.
Old ways of humanity in the cause of rainmaking have been many. Tantric methods of the East has often included weather as part of their practise. In ancient Eastern poetry, "weather talk" is code for sex and states of love and mood. Sexual energy is a very potent raw energy, and in conjunction with the tasks of the charkras can be very effective.
A pagan method of rain making, in which it is stressed to only use in an emergency, is to get a bucket of water, and get a broom (both made of as natural a product as possible), stick the handle of the broom in the bucket, and stir whilst visualising a storm. When the water is spinning, tip it on the earth. It was known in older schools of thoughts that storms, especially sudden, unexpected or unseasonal ones, is a sign of witchcraft being done.
Killing a lizard or frog is a way of causing rain according to darker forms of craft. So is pouring water on the ground, or offering wine to "the gods" by pouring a bit on the ground. Then, for the modern religious type, is to simply praying for rain, with faith, and realising that God has their own plans, although "God helps those that help themselves".
Also, in the Law of the Ironic, doing your laundry or washing your car or planning a picnic is an almost sure guarantee of rain!