Water Vapor in the Earths Atmosphere

Have you ever wondered how much water vapor is in the Earths atmosphere or what the maximum amount is that air can hold? How Much Water Vapor Is in the Earths Atmosphere? Water vapor exists as an invisible gas in the air. The amount of water vapor in air varies according to the temperature and density of air. The amount of water vapor ranges from a trace amount up to 4% of the mass of air. Hot air can hold more water  vapor than cold air, so the amount of water vapor is highest in hot, tropical areas and lowest in cold, polar regions.