What is air pressure? Air pressure is the weight of air molecules pressing down on the Earth. The pressure of the air molecules changes as you move upward from sea level into the atmosphere. The highest pressure is at sea level where the density of the air molecules is the greatest.There are large masses of high and low pressure across the Earth. There are also small changes in air pressure that affect you locally. In the borders between high and low pressures you will find storm fronts or smaller changes in weather: temperature, humidity, or cloud cover.
How does air pressure influence weather? Air pressure, or atmospheric pressure, is caused by the combined weight of a column of air directly above a point on the Earth or in the air. At high elevations such as the top of mountains, there is less air above the Earth's surface than at lower elevations such as sea level, so atmospheric pressure is lower at the top of a mountain than at sea level. Most weather maps show sea level pressure, which is the atmospheric pressure at sea level. Weather maps show atmospheric pressure using lines called isobars, which are similar to contours on a topographic map. Scientists look at the strength of these patterns to study changes in atmospheric circulation, and how these change are related to changes in temperature, precipitation and winds.