Pressure varies from day to day at the Earth's surface the bottom of the atmosphere. This is, in part; because the Earth is not equally heated by the Sun. Areas where the air is warmed often have lower pressure because the warm air rises. These areas are low pressure systems. As altitude increases, the amount of air over a unit area decreases. Therefore, the atmospheric pressure will reduce due to lower air molecules. The fall and winter seasons had the highest variability in atmospheric pressure readings. There was a significant correlation (p = 0.0083) between a decrease in atmospheric pressure and the occurrence of AMI the day after a pressure decrease, especially during the fall and winter seasons. The pressure exerted by the air in the atmosphere is greatest at Earth's surface and falls as altitude increases. The reason is that density and depth of the atmosphere are greatest at sea level and decline with increasing altitude. The atmospheric pressure is greatest at the bottom of the atmosphere. This is also where the air has its greatest density. Pressure and density decrease with height in the atmosphere. The earth's gravitational field pulls the mass of the atmosphere towards the earth's surface.