Air pressure is the amount of pressure the weight of air exerts on a specific point. In terms of weather, air pressure is measured in millibars, hectopascals or inches of mercury. For items such as tires and other inflatable items, air pressure is measured in pounds per square inch.
Air pressure varies greatly depending on elevation, temperature, climate and oceanic tides. As of 2015, the highest recorded air pressure was 1,085.7 hectopascals in Tosontsengel, Mongolia on Dec. 19, 2001. The lowest recorded air pressure was 870 hectopascals in the western Pacific Ocean on Oct. 12, 1979. Air pressure also affects the temperature at which water boils.