Wind direction is generally defined as the orientation of the wind vector in the horizontal. Wind direction for meteorological purposes is defined as the direction from which the wind is blowing, and is measured in degrees clockwise from true north.

Wind direction determines:

The transport direction of a plume or puff in air quality modeling applications

The standard deviation of the wind direction (sq) may be used, in conjunction with wind speed, to derive the atmospheric stability classes.

The wind direction is measured directly using a wind vane. The conventional wind vane consists of a tail section attached to one end of a horizontal shaft which, in turn, is mounted on a vertical axis; the tail and shaft rotate in a horizontal plane. The wind vane measures the azimuth angle[2] of the wind.