How to Interpret Barometric Pressure Readings
- 1). Determine what type of barometer you are using. Mercury or water-based barometers look similar to a thermometer, while aneroid barometers look similar to a clock, with a face and hands, called needles.
- 2). Note the point at which the mercury has risen on the scale (on a mercury barometer) or the point at which the needle crosses the scale (on an aneroid barometer). This point will correspond to a value in millibars, and this reading tells you how many millibars of pressure the atmosphere above you is exerting downward.
- 3). Determine whether the reading is low or high. If the measurement is below 1013 mb (29.92 inches), the pressure is considered "low," as it is lower than atmospheric pressure at sea level. This usually indicates stormy weather. If the measurement is above 1013 mb (29.92 inches), this means the pressure is considered "high," as it is higher than atmospheric pressure at sea level. This usually indicates fair weather.
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