Artificial rainfall can be divided into warm cloud rainfall and Leng Yun rainfall. In order to make warm clouds (clouds with temperature higher than zero) rain or increase rainfall, it is necessary to spread hygroscopic particles such as salt powder and urea in the clouds to promote the production of heavy raindrops for rainfall.
If it is necessary to rain in the Leng Yun (a cloud with a temperature below zero), it is necessary to use aircraft and other tools to spread rain agents such as dry ice and silver iodide, thus producing a large number of ice crystals, increasing the density of ice crystals in the upper part of Leng Yun and promoting the formation of rainfall.