Air Pressure

Air may seem like nothing, but it actually has weight. Air pressure is the force of air pushing down on the Earth's surface. We do not feel it because our bodies are used to it. Changes in air pressure help cause weather changes. Meteorologists watch air pressure closely to predict the weather.

What Causes Air Pressure

The atmosphere is a thick blanket of air surrounding Earth. All that air has weight, and it presses down on everything below it. At sea level, the air pressure is highest because there is more air above you. On a mountaintop, the air pressure is lower because there is less air above you.

Air Pressure and Weather

High air pressure usually brings clear, calm weather. The heavy air pushes clouds away. Low air pressure usually brings clouds and rain. The lighter air allows moisture to rise and form clouds. Weather maps show areas of high and low pressure. Winds blow from high pressure areas toward low pressure areas.

Fun Facts

• At sea level, about 14.7 pounds of air press on every square inch of your body.
• If you added up all the air pressure on your body, it equals about 20,000 pounds.
• Air pressure drops about one inch of mercury for every 1,000 feet you go up in altitude.

Did You Know?

Your ears pop on an airplane or driving up a mountain because the air pressure outside your ear changes faster than the air pressure inside. Your ear adjusts with a little pop!