How Much Water Vapor Is in the Earth's Atmosphere?

Properties of Water Vapor in the Earth's Atmosphere

Water vapor can condense to form clouds.
Water vapor can condense to form clouds, but even a cloudless sky contains some invisible water vapor. Anne Helmenstine
by Anne Marie Helmenstine, Ph.D.
Dr. Helmenstine holds a Ph.D. in biomedical sciences and is a science writer, educator, and consultant. She has taught science courses at the high school, college, and graduate levels.
Updated March 20, 2017

Have you ever wondered how much water vapor is in the Earth's atmosphere or what the maximum amount is that air can hold? Here's the answer to the question.

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.

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