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Humidity

Humidity is the amount of water vapor in the atmosphere. The higher the temperature, the greater the number of water molecules the air can hold.

Heat is needed to evaporate water, changing it into vapor in the air. This heat is called latent heat. If you leave a pot full of water boiling on the stove, the amount of water decreases as the water boils. The water molecules are changing from the liquid state to water vapor gas. There are large amounts of water vapor in the air but it doesn't usually get there by boiling water. Most of the vapor that is in the air evaporated from the surface of the oceans.

Humidity is not the same everywhere! It can change each day and is generally different in locations that have different climates. On the interior of continents, where the air is further from oceans and less able to pick up vapor from the sea surface, there is generally lower humidity than places that are near the ocean. Also, because warm air can hold more moisture than cool air, locations with warm climates, such as those near the equator, generally have higher humidity than locations with cooler climates, such as those near the poles.

Learn more about water in the air from Water, Water Everywhere!

How does water get into and out of the atmosphere?