Wind speed refers to the moving speed of air relative to a fixed place on the earth. The commonly used unit is m/s,1m/s = 3.6 km/h. Wind speed has a grade only if there is no grade, and wind speed is the basis for classifying wind grades. Generally speaking, the greater the wind speed, the higher the wind level and the more destructive the wind is. Wind speed is one of the main parameters in climatology research, and the measurement of atmospheric travel plays an important role in global climate change research, aerospace industry and military application.

Wind has both magnitude and direction, so the wind forecast includes wind speed and direction. The magnitude of wind speed is usually expressed by wind grade. The level of wind is determined according to the degree of influence of wind on ground objects. Meteorology is generally divided into seventeen grades according to the magnitude of wind.