My barometer pressures have dropped from about 1010 yesterday to 970 on my traditional barometer and 959 on my electric weather station. There is always a discrepancy of about 10 (millimeters of Mercury?) between the two.

What is ‘pressure’. Pressure is air pressure, the weight of the air pressing down on us from the top of the atmosphere downwards.

The guage on the traditional barometer has gone from fair (gold pointer) to rain with the black pointer.

How is pressure measured? One ‘bar’ of pressure is the average air pressure at sea level. It’s also measured in millimetres of Mercury.  There was a historical experiment to find out about the air pressure. The experimenters put a tube of  mercury upside down in a glass dish. This can leave a vacuum in the top of the tube. If you have the tube and dish at sea level the Mercury will be at a lowed level in the dish. This is because a larger weight of atmosphere is pressing down. Go up a mountain and the level in the dish will rise, because the air pressure up there is lower (less depth of atmosphere).

There is lots of information on sites like Wikipedia about air pressure. They probably describe how the air circulating in the atmosphere causes areas of low and high pressure. The weather is also influenced by the sea and its temperatures and the heating of the Earth’s surface by the sun.