A barometer is a scientific instrument used to measure atmospheric pressure, also called barometric pressure. The atmosphere is the layers of air wrapped around the Earth. That air has a weight and presses against everything it touches as gravity pulls it to Earth. Barometers measure this pressure.

How does a barometer predict weather?

Weather forecasters use a special tool called a barometer to measure air pressure. Barometers measure atmospheric pressure using mercury, water or air. ... Forecasters use changes in air pressure measured with barometers to predict short-term changes in the weather.

How does the barometer work?

How does a barometer work? Simply put, a barometer acts like a balance that 'balances' the weight of the atmosphere (or air around you) against the weight of a mercury column. If the air pressure is high, the mercury will rise. At low air pressure, the mercury goes down.