Barometric pressure data are widely available and include both current pressures and historic barometric pressure readings. Websites worldwide provide weather reports and isobar maps to monitor shifts in barometric pressure. Local TV and radio stations give frequent and regular readings of pressures. Government agencies, especially those heading emergency response teams, provide up-to-the-minute data when severe weather is on its way. Campers can use weather radios to track changes in pressure. Frequent checks on your barometer can keep you abreast of weather trends. No matter how you find barometric pressure, if it's changing quickly, a change in weather is on its way.
Note the scale on your barometer. It may be in inches, millimetres, or hectopascals. Inch scales range from 28.5 to 31.5, millimetre scales from 700mm to 800mm, and hectopascal scales from 990 to 1040. All barometers should be sectioned off for "Rain," "Change," and "Fair."
Tap the glass face of the barometer to free the internal linkage mechanism. This should ensure proper functioning of the sweep arms.
Notice that your barometer has two arms. One is the set arm, the other is the reading arm. The reading arm usually is longer and may look like an arrow. Read the number that lines up with the reading pointer to find the current barometric pressure. Note also in which area the number falls.
Connect to the Internet and go to a weather website. You can look up historical data, barometric pressure readings from your geographical area, and readings from most areas worldwide. Some sites show maps with isobar pressure lines drawn so you can see the pattern. Other sites give you a number readout for a specific location.
Call your local television or radio station's weather hot line for updated weather information. The barometric pressure is a common reading that is included in weather updates, especially during hurricane season.
Listen to your emergency broadcast networks for important updates on the weather. Barometric pressure can change rapidly when a front arrives or when a hurricane approaches. Pay attention especially if precautionary measures are advised.
Locate a digital barometer. Digital barometers output pressure readings in digital format.
Be aware that first you'll need to adjust your barometer for your altitude. Most barometers made prior to 1986 used the millibar scale; one hectopascal is equal to one millibar.
Quick changes in barometric pressure mean a change in weather is imminent; tune in to your local weather station for more information.