The Bible teaches that before the flood a canopy of water (firmament) surrounded the earth. This canopy is mentioned in Gen. 1:6&7, Psalms 148:4 and II Peter 3:5. The Creation Account in Genesis 1 records that a mist that went forth and watered the face of the whole ground. Genesis mentions no other precipitation until the flood brought rain for 40 days and 40 nights. Many people teach that rain never fell before the flood. Although that is probably true, it cannot be taught dogmatically because the Bible simply does not mention the subject. Possibly if the canopy of water mentioned in Genesis 1:6 and 7 increased the air pressure, as many think it did, rain would probably not fall.

It may be that Noah was preaching that rain would come out of the sky (something that had never happened), and the people laughed just like today when Christians preach that Jesus will come out of the sky (something that has never happened) to catch up all believers in Christ (See Matthew 24:37, Luke 17:26 and I Thess 4:16).