Before rain
Before there was rain, a mist went up from the land and watered the whole face of the ground. (Genesis 2:6)
Rain is used to destroy all flesh
God destroyed all flesh apart from Noah and those who were with him in the ark through a bursting of the fountains of the great deep, an opening of the windows of the heavens, and 40 days and 40 nights of rain. The waters were so great they covered 15 cubits over the mountains and killed all flesh on earth apart from those who were with Noah in his ark.
God remembers Noah and restrains the rain
Then God remembered Noah and all the beasts and livestock in the ark, and God restrained the rain from the heavens. The waters receded from the earth continually until the 27th day of the 2nd month of 601st year of Noah, when the earth had dried out.
(Genesis 8)
God resolves never again to strike down all living creatures as He had done
Then Noah built an altar to the Lord and took some of every clean animal and some of every clean bird and offered burnt offerings on the altar. When the Lord smelled the pleasing aroma, the Lord said in his heart, “I will never again curse the ground because of man, for the intention of man's heart is evil from his youth. Neither will I ever again strike down every living creature as I have done. While the earth remains, seedtime and harvest, cold and heat, summer and winter, day and night, shall not cease.”
(Genesis 8)