In the Name of Allah, Most Gracious, Most Merciful.
All thanks and praise are due to Allah and peace and blessings be upon His Messenger.
Dear questioner, may Allah bless you for your question and your search for true knowledge and an understanding of your faith.
It should be highlighted, first of all, that nobody, whatever be his power or might, can claim to have access to the knowledge of Allah or to have special abilities that enable him do things that nobody else can do.
Whatever is used by the scientists to generate the artificial rain, namely the chemical substances, is no more than a creation of Allah, which makes the whole issue of generating such artificial rain fall under the great power of Allah and His Will, and makes the people no more than tools to carry out the Will of Allah and demonstrate His Power, for He created them and their creative minds and guided them to what brings benefit to mankind.
A true believer, when he finds such new technologies and achievements, will trace them back to Allah, Who creates then disposes, Who measures then guides. Whenever a Muslim sees such new things, he will automatically remember the verse: “We shall show them Our portents on the horizons and within themselves until it will be manifest unto them that it is the Truth. Doth not thy Lord suffice, since He is Witness over all things?" (Fussilat: 53)
Elaborating on this point, Sheikh `Attiyah Saqr, a prominent Azharite scholar, states:
"It is agreed upon that the condensation of vapor in the clouds happens due to certain reasons, which in turn lead basically to the fall of rain. This process is the sole task of Allah, Who said: “He sendeth down the rain." (Luqman: 34) It is Allah Who allows the reasons to work out and lets the whole process succeed. He could, if He wanted, cripple the reasons and make them non-effective. It is He Who created the vapor, the heat, the cold, and the rays of the sun. It is also He Who sends the wind and moves the clouds from one place to another. This is all His, and nobody can claim power in this. Allah says: “Hast thou not seen how Allah wafteth the clouds, then gathereth them, then maketh them layers, and thou seest the rain come forth from between them; He sendeth down from the heaven mountains wherein is hail, and smiteth therewith whom He will, and averteth it from whom He will." (An-Nur: 43)
In cases where scientists try making rain, it is all based on certain natural processes created through evaporation and condensation. These scientific operations, in no way, represent an interference in the creation of Allah, simply because the substances and processes used in them are the creation of Allah. Nobody can claim the ability to create heat or cold himself without the use of some apparatus.
It should be noted, however, that the results of such attempts are not promising because in these countries people are still complaining of drought and barrenness. This all gives evidence to the fact that the Power of Allah exceeds their Power and His Will overpowers their will. It resembles the case when a doctor heals a sick person. Allah is still the Healer and the doctor is just the tool.
In addition to those scientists’ inability to keep their countries in continuous rains, they can in no way stop storms, thunder, floods, volcanoes or earthquakes. With all their civilization and scientific and technological advancement, they are still dependent on the help and assistance of Allah. Almighty Allah says: "O mankind! Ye are the poor in your relation to Allah. And Allah! He is the Absolute, the Owner of Praise. If He will, He can be rid of you and bring (instead of you) some new creation. That is not a hard thing for Allah" (Fatir: 15-17)"
Almighty Allah knows best.
