Weather Vane, or Wind Vane, a device that shows the direction of the wind. A common type is an arrow fixed to an upright rod that is able to rotate freely, so that the arrow always points into the wind. The cardinal points of the compass also are usually shown on weather vanes. A large weather vane at an airport is called a wind tee. At airports and landing strips, wind direction may be shown also by a cone-shaped bag called a wind cone, wind sleeve, or wind sock.
To be accurate, a weather vane should be placed well above the ground in a position in which it will not be disturbed by wind deflected from other objects.