This is paper presents significance of vertical wind shear. Voltage flicker that may be initiated in the output of the horizontal axis upwind wind turbine located at any given site for a given tower height and blade length. Vertical wind shear is one of the important parameters which instigate voltage flicker in wind turbine output voltage. In this paper diverse origins of flicker, places where wind shear occurs, computation of wind shear, general impacts of wind shear, impact of wind shear on wind turbine output is discussed. © 2017 IEEE.