Weather vane or wind vane, instrument used to indicate wind direction. They are typically used as an architectural ornament to the highest point of a building. It consists of an asymmetrically shaped object, an arrow or a rooster, installed at its center of gravity so it can move freely about a vertical axis. These instruments consist of a rotating bauble that points the direction at the top of a rod. The weather vane usually comprises of a small globe at the top of the stable section of the rod and a larger globe is attached at the bottom. A directional that indicates north, south, east and west is usually affixed to the rod between the two globes. These instruments have been in use for centuries, dating from around 50 BC. They were probably the first instruments ever used to measure and predict the weather.
Andronicus who was an astronomer built history’s first recorded weather vane for the Tower of the Winds in Athens. Bronze weather vanes have been found by archaeologists among 9th century Viking ships’ remains. In the 9th century, the pope is said to have ordered that every church steeple show a clock, making the rooster a popular icon in weather vanes. Weather vanes are used in Britain, Normandy and Germany to show archers the direction of the wind.
A weather vane points in the direction opposite to the direction of wind. For example, if the wind is coming from the east, the arrow will point to the east. This would mean that if you were to face east, you would feel wind on your face.
If your weather vane changes from west to east this may be a signal that a mass of lower pressure is above and will bring storms. If the weather vane indicates a shift from the south or southwest, this may indicate that warmer air is on the way. If the wane is swinging erratically, this means the air is unstable and the current weather conditions are changing.