Water vapor gets into the air through evaporation.
These all act to increase the amount of water vapor in the air. Water vapor can also be transported from places nearby and far away. Winds carry moisture-laden air from ocean areas toward land, where the air would otherwise be dry. Similarly, Arizona's summer rainy season is directly linked to the transport of air with a high water vapor content from the Gulf of California and points south. The dew point of air can be decreased in the opposite ways.