Then remove your thumb and quickly put the mouth of the bottle into the saucer of water. Now you can chart whether the water goes up or down in the bottle. The water does not pour out of the bottle. Instead, the water level drops slightly and comes to rest. Then, it moves up or down as the air pressure changes.
Air pressing against the water prevents it from running out.
The water stops moving downward when the pressure of the atmosphere balances the water pressure. When there is a decrease in the air pressure, the water level drops. An increase sends the water up. When the water in the bottle drops down, you can expect warmer, wetter weather. When the water goes up, it will be drier and colder.