The symbols 'Sun' and 'Rain' (or the text on the dial 'Rain' and 'Fair') are conventionally positioned on the display of the analog barometer. 'Sun' is located on the right side within the 'High Pressure' range, while 'Rain' is placed on the left side within the 'Low Pressure' range.
These indications or symbols often lead to misunderstandings when using an analog barometer. Here is the clarification:
The symbols are intended to merely suggest that when the pointer moves to the right (indicating an increase in air pressure), the weather is likely to improve. Conversely, when the air pressure decreases, the pointer moves towards the left (in the direction where the 'Rain' symbol is positioned).
It is important to note that it is entirely possible for the sun to shine when the air pressure is low (pointer on the 'Rain' symbol) and for rain to occur when the air pressure is high (pointer on 'Sun').
As previously explained, the critical factor with an analog barometer is not the current position of the pointer but the direction it has moved over a specific period. To achieve this, one sets the reference pointer to the current value and regularly reads the value over a designated time (e.g., every 12 or 24 hours). By observing the direction in which the pointer moves, one can make a weather prediction. If the barometer's pointer remains stationary (common in summer), it suggests that the weather is unlikely to change. Occasionally, there may be minor fluctuations in air pressure. To detect these, it is advisable to tap the glass of all analog barometers lightly before reading. This tapping ensures slight movement of the pointer, allowing for the observation of these subtle changes and an accurate determination of the actual direction in which the pointer is moving.