Assalamualaikum Warahmatullahi Wabarakatuh

In the name of Allah, the Entirely Merciful, the Especially Merciful. O Allah! I seek refuge in You from knowingly associating partners with You in any way, and I seek Your forgiveness for that which I do not know. Ameen.

The benefits of rain in Islam are many for human life and other living beings on earth. Rain is the grace of Allah s.w.t. which humanity should be grateful for. 

In the Qur'an, the benefit of the rain sent down to the earth is to fertilize the barren and dry land, so that plants grow from this land. The plant is then beneficial to the life of living beings and spoils the eyes of anyone who looks at it. 

Allan s.w.t. said: 

"And among His signs (is) that you see the earth dry and arid, then when We send water on it, it moves and grows fertile. Verily God Who Lives it, must be able to bring the dead back to life.  Indeed, He has power over all things." (QS. Fushshilat: 39). 

The rain sent down to earth is also something blessed. Allah s.w.t. said: 

"We send down from the sky blessed water (many benefits) and We grow with that water the trees and the seeds of the harvested plants" (QS. Qaf: 9). 

Rainfall Process 

In Surat An Nur verse 43 Allah s.w.t. says: 

"Don't you see that Allah marches the clouds, then gathers them between (parts), then makes them overlap, then you see rain coming out of the gaps and Allah (also) sends down (particles of) ice from the sky, (  that is) from (clods of cloud like) mountains, then He casts (particles of) ice on whom He wills and turns them away from whom He wills. The lightning of the cloud almost disappears  vision. God alternates night and day. Indeed, in such a thing there is a great lesson for those who have vision".  (QS. An Nur: 43). 

Ibnu Katsir explains that Allah s.w.t. asserts that He is the one who drives the clouds with His power since the beginning of its formation which is still thin. Then collect between (the parts). 

That is, bringing it together after being separated. Then make them overlap. That is overlapping, some of them overlap some of the others, then you can see the rain coming out of the cracks". 

In Surat Al Baqarah verse 22 also mentioned about rain. 

"He (Allah) sends down water (rain) from the sky, then He produces with that rain all the fruits as sustenance for you. Therefore, do not associate with Allah, even though you know". 

Through the rain, Allah s.w.t. grows for them various kinds of plants that produce many kinds of fruit, as has been witnessed. It is a sustenance for them, also for their livestock. 

Wallahu A'lam