How does atmospheric pressure help weather and breathing work?

Air has mass, so the atmosphere exerts pressure on Earth’s surface. At sea level, average air pressure is about 1013 hectopascals, or 1 atmosphere. Differences in pressure between regions help create winds and storms as air moves from high pressure to low pressure. In the human body, breathing works because the diaphragm changes chest volume, lowering pressure in the lungs so air flows in. Atmospheric pressure also changes with altitude, which is why breathing becomes harder on high mountains.