what does a falling barometer indicate

What does a falling barometer indicate? Using a barometer is not all that tricky, but you need to know what those readings indicate.

A change in the reading indicates a change in the weather patterns, which helps you understand how to plan ahead.

But, many people ask, what does a falling barometric reading of atmospheric pressure indicate? So, what do you think?

In reality, a falling barometer indicates a low-pressure weather system is moving in, which means it might rain at any time. 

Learning More about a Barometer

learning more about a barometer

A barometer is a scientific instrument designed to indicate changes in air pressure.

Barometers are useful for predicting the weather over the short-term and use atmospheres (atm) as their standard unit of measurement.

Fact: One atm equals the weight and force of air, the pressure, when at 15 degrees Celsius (59 degrees Fahrenheit) and at sea level.  

More about the Types of Barometers

There are different kinds of barometers, mercury, replacing a prototype made using water, was developed in 1643.

The aneroid, from 1844, was a sealed container that would rise and fall as the pressure changed.

more about the types of barometer

And of course, the modern digital, which is not unlike the GPS on a Smartphone.

Moreover, a barograph is a barometer that takes a continuous reading. 

Importance of Barometer in Measuring Atmospheric Pressure

A wide variety of scientific disciplines rely on accurate measurements of air pressure for their work, and some of them include:

  • Atmospheric science
  • Physics
  • Chemistry

In both the lab and the outdoors, barometers are used to monitor atmospheric pressure, providing valuable information for scientific study.

But there are other reasons why barometers are essential.

For instance: 

Understanding Weather Patterns

understanding the weather paterrns

Changing atmospheric pressure can be an early indicator of a shift in the weather.

Therefore, it is important to keep an eye on it if you are trying to decipher weather patterns.

Better weather forecasts are possible thanks to barometers, which measure changes in air pressure. 

Using in the Aviation Sector

using in the aviation sector

Air pressure variations can have serious consequences for the transportation industries, including aviation and shipping.

And barometers help a lot here.

They are used to detect and track atmospheric pressure fluctuations that might cause severe weather like hurricanes and tornadoes

Determining Altitudes

To ascertain altitude, changes in air pressure can be used for assistance.

Hence, if an airplane’s altitude drops as the pressure rises, it may mean it is moving up, and the opposite would be true for a descent. 

What Does a Falling Barometer Indicate?

A rise in the barometer reading is the signal of high air pressure and fair weather.

On the other hand, a fall indicates the air pressure is falling and colder air, clouds and possibly rain are approaching. 

Understanding Barometric Reading

understanding the barometric reading

Apart from the digital, which uses sensors, all traditional barometers work on the same principle.

It means an increase or decrease in air pressure will force liquid up or down a tube.

Understanding the readings on a barometer allows us to make general predictions about the weather.

However, the barometric pressure provided by a barometer is only a measure of the air pressure at its location.

It means it measures only the weight of the column of the atmosphere that is pressing down from directly above.

This weight or density changes according to temperature and altitude which causes the barometer readings to rise or fall. 

Learning More about Falling Barometric Reading

learning more about falling barometric reading

As mentioned already, a falling barometer indicates decreasing low pressure.

The density of the atmosphere is increasing and the air pressing down onto the barometer from the column above is now heavier.

It means it has more mass with more water vapor.

Continuing to fall is an indication that weight is continuing to be added and the pressure is still lowering as the air density is increasing. 

Deciphering a Falling Barometer

A barometer that is falling is reacting to the lowering air pressure created by cooler air falling onto the earth’s surface.

Because air density is also affected by temperature, a barometer may rise and fall several times throughout the day.

It is worth mentioning that air density, temperature and pressure are indicators of the state of the weather.

And as barometers are location specific, they are a useful tool for predicting short-term changes. 

Calibrating Barometer to Understand a Fall in Barometric Reading

calibrating barometer

With the aid of a scale, a barometer is calibrated to show what sort of weather to expect using a dial and an indicator needle.

As the atmospheric pressure changes, the indicator needle moves as the liquid is forced up and down the tube.

This often shifts clockwise or counterclockwise to the corresponding typical weather condition displayed on a dial.

Fact: Any reading below 29.80inHg is low and associated with warm, rising air and rainstorms. 

The Scientific Outcomes of a Falling Barometer

scientific outcomes of a falling barometer

Being able to use a decorative dial is only possible because we know what set of conditions are most likely to create each kind of weather.

For scientific use in meteorology, mercury barometer readings are taken in inches of mercury (inHG)

A falling barometer predicts incoming bad weather.

The rate of the fall is an indication of how fast the atmosphere around the barometer is changing. 

The Change in Density with a Change in Barometric Reading

density changes with barometric reading

Density increases as the water vapor suspended in it condenses into droplets in higher cool air.

The further the fall, the worse the predicted weather. For example, the mercury level reads 30.20 inHG but begins falling steadily as clouds form.

As the density increases due to the growing weight of gathering droplets suspended within it, the pressure drops further and the mercury falls faster.

Under 29.80 inHG there is an increasing likelihood of rain. A rapid descent indicates a storm is building and likely to hit within a day. 

Wherever the mercury level holds steady, the weather is set to stay as it is for a while. 

Situations When You Get a Falling Barometric Reading

light winds with gusts

Examples of situations where a falling barometer is observed are:

  • The arrival of a low-pressure weather system created by rising warm wet air.
  • Light winds with gusts as the denser heavier air pushes the less dense air out of the way.
  • A fall in surface temperatures as the cooler air drops to the ground.
  • Winds blowing towards the center of the system to try and equalize the pressure.
  • Clouds forming as water vapor cools to droplets at altitude.
  • Heavy cloud cover as each drop coalesces with others.
  • Precipitation, as the droplets grow too heavy for the air to support them and fall. 

Understanding the Effects of a Falling Barometer

Humans don’t tend to fair as well once the barometer starts falling. And it becomes evident in many ways.

For instance: 

An Arthritis Flareup

an arthritis flareup

The low pressure it indicates has had a long association with arthritis causing flare-ups of inflammation as the joint fluid reacts to the falling pressure.

The fall allows human tissue to expand in effort to take in more oxygen, but the dilating blood vessels cause swelling and pain.

Additional Symptoms

People experience headaches and nausea, and other symptoms, such as:

  • Fatigue
  • Dizziness
  • Shortness of breath
Fact: An abrupt change in atmospheric pressure can cause serious problems, as some people may experience a swelling in the brain or lungs causing life-threatening edema. 

Real Life Impact of Changing Barometric Reading

Traditional barometers are sensitive instruments, they react to the conditions around them losing accuracy when placed in the sun or near an open window.

But they were and are, essential equipment for those in the fishing and agriculture industries.

It is accepted that fish become more active in times of falling barometric pressure and will move off into deeper water if it keeps falling.

impact of barometric reading changes in industries

These days, it is digital barometers that provide a mass of location specific weather data to many other industries, including:

  • energy suppliers
  • construction
  • transport
  • aviation
  • leisure and sport
  • those reporting the local daily weather.   

The Impact of Global Warming on Barometric Readings

There was a time when preparing for the weather predicted by a falling barometer meant making sure you had an umbrella.

That was before climate change and modern science agrees that our warmer climate will also be wetter.

However, time has run out. Governments are being forced to prepare for weather extremes.

In the US this means areas experiencing heavier downpours, fiercer storms and frequent hurricanes while others get to deal with long term drought.

Fact: There is a rule that states that with every degree Fahrenheit increase in air temperature, the atmosphere can support another 4% of water. 


What does a falling barometer indicate? It tells you that a low-pressure system is in the making and the weather is likely to change very soon.

In most cases, you may witness heavy rains as well. The opposite is true when you notice barometric reading going up.

So, it is important to understand how to read it properly and draw a conclusion accordingly.