A barometer is a scientific instrument used to measure atmospheric pressure, also called barometric pressure. ... Barometers measure this pressure. Atmospheric pressure is an indicator of weather. Changes in the atmosphere, including changes in air pressure, affect the weather.

What do the readings on a barometer mean?

A barometer measures air pressure: A "rising" barometer indicates increasing air pressure; a "falling" barometer indicates decreasing air pressure. ... If you've read How Hot Air Balloons Work, you know that hot air is less dense (lighter) than cooler air.

What is a good barometric pressure reading?

Hg. 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).