Barometric Pressure Explained


Barometric pressure normally fluctuates. Rises in pressure can be linked to clear weather. Falling pressure can be linked to wet weather or storms. Steady barometric pressure readings indicate that the current conditions will continue. 

Did you know that air has weight? At sea level, every square inch column of air weighs an average of 14.7 pounds, according to Acurite. That weight increases or decreases with changes in altitude and temperature.

What Is Barometric Pressure

Barometric pressure — also known as atmospheric pressure — describes the weight of the air surrounding the earth. The layer of air that scientists can measure with reasonable accuracy extends around 25 miles up, according to LiveScience. The portion of the atmosphere that sustains life only extends for three miles. The higher up you go, the lighter the weight of the air. 

For example, many people believe that altitude sickness is caused by a dip in oxygen levels. In mountain towns with altitudes of 8,000 feet or more above sea level, the amount of oxygen in the air is the same as the air at sea level. The difference is the air’s pressure and density. At high altitudes, there’s less pressure. That means less air is pushing into your lungs, and less oxygen is going through your bloodstream.

Why It Matters

Changes in the barometric pressure can help scientists observe and predict weather. It also affects the way gases like oxygen dissolve in water. Changes in barometric pressure can affect water levels in lakes and their estuaries. 

Researchers discovered that the air mass above land has a different temperature than the air above oceans. ThoughtCo notes that those differences are the driving force behind the development of weather systems. Meteorologists often talk about the weather in terms of high- or low-pressure systems. When there’s a storm moving in, it’s associated with a low-pressure system. High-pressure weather systems are associated with dry, fair weather.

How to Measure Barometric Pressure

Barometers have been around since the 1600s. These devices measure barometric pressure. There are two types. Aneroid barometers feature a vacuum chamber connected to a diaphragm. When pressure increases, it presses on the diaphragm. The diaphragm moves a needle on a dial, giving you a reading of the barometric pressure. 

Digital barometers also have a diaphragm. It’s attached to a strain gauge. As the pressure exerts force on the diaphragm, it changes the current running through the strain gauge. That gives the barometer its reading.h

What’s Normal?

The standard pressure at sea level averages 14.7 pounds for every square inch of air, according to SETRA. But when you’re taking readings at home or listening to weather professionals, it’s typically measured in inches of mercury (inHg). Curious about how to interpret readings?

Barometric Pressure Higher Than 30.20 inHg

If the pressure is steady or rising, you can expect fair weather to continue. If it’s slow dropping, fair weather’s on its way. If it drops quickly, expect cloudy conditions and warmer temperatures.

Barometric Pressure of 29.80 to 30.20 inHg

If the pressure is steady or rising, expect the current conditions to stay the same. If the pressure drops slowly, there will be minimal change. If the pressure drops quickly, expect rain or snow.

Barometric Pressure Lower than 29.80 inHg

If the pressure is steady or rising, expect the weather to clear with cooler temperatures. If it’s dropping slowly, rain is on the way. If the pressure drops quickly, expect a storm.

Benefits of Having a Barometer

Keeping a watch on the barometric pressure can help you better plan outdoor activities. It also can help you choose the best times to go hunting or fishing. It can even help manage headaches and other ailments that are sensitive to changes in pressure. Joint pain and migraines are two examples.