5 And every plant of the field before it was in the earth, and every herb of the field before it grew: for the LORD God had not caused it to rain upon the earth, and there was not a man to till the ground.
6 But there went up a mist from the earth, and watered the whole face of the ground.
This indicates that there had been no rain at this time and man had not yet been created. It also suggests a different form of water cycle before the Flood. The description sounds much like a dew type phenomenon; possibly resulting from a denser atmosphere; where evaporation occurred during the day and condensing to a mist a night that fell to ground.