The barometer works by balancing the weight of mercury in the glass tube against the atmospheric pressure, much like a set of scales. ... In areas of high pressure, air is sinking toward the surface of the earth more quickly than it can flow out to surrounding areas.

What does barometric pressure tell you?

Atmospheric pressure is an indicator of weather. Changes in the atmosphere, including changes in air pressure, affect the weather. Meteorologists use barometers to predict short-term changes in the weather. A rapid drop in atmospheric pressure means that a low-pressure system is arriving.

Is 30 barometric pressure high or low?

A barometer reading of 30 inches (Hg) is considered normal. Strong high pressure could register as high as 30.70 inches, whereas low pressure associated with a hurricane can dip below 27.30 inches (Hurricane Andrew had a measured surface pressure of 27.23 just before its landfall in Miami Dade County).