Genesis 2:4 - 8 New Revised Standard Version

In the day that the Lord God made the earth and the heavens, when no plant of the field was yet in the earth and no herb of the field had yet sprung up - for the Lord God had not caused it to rain upon the earth, and there was no one to till the ground; but a stream would rise from the earth, and water the whole face of the ground then the Lord God formed man from the dust of the ground, and breathed into his nostrils the breath of life; and the man became a living being. And the Lord God planted a garden in Eden, in the east; and there he put the man whom he had formed.

Rain is the first specific weather word used in the Bible. It occurs in the creation story emphasising that water is essential for the continued existence of all living things.