So if you faithfully obey the commands I am giving you today — to love the LORD your God and to serve him with all your heart and with all your soul — then I will send rain on your land in its season, both autumn and spring rains, so that you may gather in your grain, new wine and oil. I will provide grass in the fields for your cattle, and you will eat and be satisfied.
Be careful, or you will be enticed to turn away and worship other gods and bow down to them. Then the LORD’s anger will burn against you, and he will shut the heavens so that it will not rain and the ground will yield no produce, and you will soon perish from the good land the LORD is giving you. Fix these words of mine in your hearts and minds; tie them as symbols on your hands and bind them on your foreheads. Teach them to your children, talking about them when you sit at home and when you walk along the road, when you lie down and when you get up. Write them on the doorframes of your houses and on your gates, so that your days and the days of your children may be many in the land that the LORD swore to give your forefathers, as many as the days that the heavens are above the earth.

And now the modern version, taken from meteorological sciences.

To produce more rain in arid zones it is necessary to take care that more moisture is transported by the winds than normally. That is easily done by technical means. Evaporation of seawater by spraying tiny drops into the air there, where the wind blows into the land will do the job on hot days, leaving the salt behind. Ideal geography is the Suez Canal, the coasts of Red Sea, the Horn of Africa etc.

Each ton additionally evaporated water will come down within few days as fresh water rain far off the coast line. The cost per ton is about 1 Euro-Cent.