Weather apps provide tons of information, but you might only check the temperature and precipitation. Other metrics can give you a better idea of how the weather will actually feel. Barometric pressure—or “air pressure”—is one of them.
The current temperature is not always a great indicator of how it really feels outside. Humidity plays a big role in this, and we’ve talked about how dew point is what you should really be looking at. Barometric pressure is another oft-ignored metric that can play a big role in not only how the weather feels but how you feel.
What Is Barometric Pressure?
Barometric pressure—also known as “air pressure” or “atmospheric pressure”—is the measurement of gravitational pull on gases in the atmosphere. The air around us has weight to it, but that weight varies depending on a variety of factors.
Atmospheric pressure is usually measured with a barometer—hence the name “barometric pressure.” A barometer contains mercury inside of a glass tube, and the mercury rises or falls with the weight of the air pressure. The pressure is then described by how high the mercury rises.
The biggest factor that affects air pressure is altitude. The higher above sea level you get, the lower air pressure becomes. And as that pressure drops, so does the amount of oxygen in the air. That’s why it’s harder to breathe at the top of very tall mountains.
Air Pressure and Weather
What does air pressure have to do with weather? Air pressure can tell us what kind of weather is coming. You’ve probably heard terms like “low pressure system” and “high pressure system.” The “pressure” part of those terms is a reference to barometric pressure.
Low pressure systems are caused by warm temperatures, and they usually bring storms, wind, and precipitation. On the other side of the coin, you have “high pressure systems.” These are caused by cool temperatures, and it usually means sunny, clear weather.
There are a number of different units used to denote air pressure. Two of the most common are “inches of Mercury” (inHg) and “Millibars.” Many weather apps allow you to choose the unit you’d like to use for pressure.
The cool thing about air pressure is you can use it to predict the weather. Once you know how to read a barometer, you can easily know what type of weather to expect.
High Pressure
When the barometric reading is over 30.20 inHG, you can expect calm weather. Rising and steady pressure in this range means the fair weather will continue. Rapidly dropping pressure in this range means cloudy and warmer weather.
Normal Pressure
The “normal” pressure reading is around 29.80 to 30.20 inHg. This range is typically associated with steady, consistent weather. Rapidly dropping pressure in this range means rain or snow is likely.
Low Pressure
A reading below 29.80 inHg is considered low pressure. Rising and steady pressure in this range means cooler, clear weather is coming. Slowly falling pressure in this range usually means rain. Rapidly dropping pressure below 29.80 inHg indicates a storm is coming.
Air Pressure and Your Body
Barometric pressure doesn’t only affect the weather, it can affect how you feel, too. Remember, air pressure measures the weight of the air, and that air is all around us.
Air pressure changes have been shown to play a part in triggering migraines. Cynthia Armand, MD, an assistant professor of neurology at Montefiore-Einstein, explained:
“Our head is made up of pockets of air that we call sinuses. Usually, those pockets of air are at equilibrium with the atmospheric pressure. When there’s a change in that atmospheric pressure, it creates a change in what you’re experiencing in your head and what’s going on in the air around you. That shift is a migraine trigger.”
When the change of pressure comes with lightning, it’s even more likely to trigger migraines. According to a study in 2013, if there was lightning within 25 miles of the individual, there was about a 25-30% increased risk of a new headache.
Beyond migraines, air pressure can also affect your blood pressure, the ability to control your blood sugar, and cause joint pain. People who say they can “feel weather changes” are most likely referring to air pressure changes.
Air Pressure in Weather Apps
The majority of weather apps include an air pressure reading. The Apple Weather app on the iPhone and iPad has a “Pressure” module with a handy dial to show if the air pressure is high or low. Many iPhone weather apps include pressure.
Google’s lackluster weather web app lists the weather, but it’s a rounded number. You’re better off with a different weather app if you’re an Android user. The Weather Channel app, for example, lists the pressure and an arrow to indicate high or low.
Air pressure isn’t generally something that updates frequently in a weather app. You only need to check once or twice a day to keep an eye on fluctuations. Once you get a feel for the air pressure in your area, you’ll be able to know what the weather’s going to do. Now you’re the meteorologist!
RELATED: Forget Humidity, Dew Point Is How It Really Feels Outside
