God had "withheld the waters" in the primeval "waters which were above the firmament" (Genesis 1:7), so that there was no "rain upon the earth" (Genesis 2:5) in the antediluvian period. But then, when their iniquity was full, He "sent them out" and they "overturned the earth."

Source:

KJV Defenders Study Bible, by Dr. Henry Morris, Ph.D.
Publisher: Thomas Nelson
Language: English
DEF 10 ISBN 0-529-10444-x
DEF 10-1 ISBN 0-529-10445-8