Why can we not generate artificial rain ?

Soon after the arrival of summer ,several areas are declared drought affected and allowances are given .We can't generate rain artificially .The artificial raining process is that normal rain clouds can be induced to rain

          The water present in the rain clouds is in vapour state .Rain  is formed when vapour is condensed into water drops .The dust particles help to form rain . The vapour cools with each dust particle as a centre and comes down as rain drops

           But if there are not enough dust particles in the atmosphere rain clouds are not converted into rain .Rain is created artificially by scattering crystals of chemicals like silver iodide in the clouds with the help of aeroplanes .This process is called seeding .This is a very expensive process .Moreover , the chances of success are often very remote .That is why we cannot employ this technique often .