CE led color screen thermometer weather station with clock
Firstly , you need to understand what atmospheric pressure that is barometric pressure is. This is very simply the weight of the air mass that is sitting on top of your location. The pressure that this air exerts on you is generally measured in inches of mercury here in the US, other parts of the world may use millimeters of mercury, Torr, kilo Pascals, or millibars depending on where you live. The units used really don't matter from a weather forecasting standpoint, all that is really necessary is to know that small variations in the barometric pressure can result in big changes in the weather.
Low pressure generally brings rain. In areas of low air pressure, the air is less dense and relatively warm, which causes it to rise. The expanding and rising air naturally cools, and the water vapor in the air condenses forming clouds and the drops that fall as rain. Conversely, in High pressure areas the air is more dense and relatively cool, which causes it to sink. The water vapor in the sinking air does not condense, leaving the skies sunny and clear.
A weather station need outdoor temperature and humidity sensors. Using the information supplied by these instruments the weather station can make fairly accurate predictions of approaching weather. The weather stations that Chaney Instruments manufactures incorporate a special learning mode so that they will automatically compensate for the altitude in your location.