Barometric pressure is the weight of the overlying air pressing down on the earth. Low barometric pressure means the overlying air is rising, whereas high pressure means the overlying air is sinking. A barometric reading below 29.80 inHg is generally considered low, and low pressure is associated with warm air and rainstorms. A barometric reading in the range of 29.80 and 30.20 inHg can be considered normal, and normal pressure is associated with steady weather. A barometric reading over 30.20 inHg is generally considered high, and high pressure is associated with clear skies and calm weather.

Changes in barometric pressure correspond to changes in weather, and pressure extremes are often associated with extreme weather events. A rising barometer indicates increasing air pressure, while a falling barometer indicates decreasing air pressure. High barometric pressure supports sunny, clear, and favorable weather conditions, but lower levels promote rainy and cloudy weather conditions.

In summary, low barometric pressure refers to a reading below 29.80 inHg, and it is associated with warm air and rainstorms.