CBSE Class 7 Answered

Wind is nothing but air in motion. Wind is produced by the uneven heating of the earth’s surface by the sun. Since the earth’s surface is made of various land and water formations, it absorbs the sun’s energy unevenly. Also, there is uneven heating between the poles and equator of the earth.  
As the sun warms the Earth's surface, the atmosphere around it also becomes warms. Since warm air is lighter than cold air, it rises. Then the cool air moves in and replaces the rising warm air. This movement of air is what makes the wind blow. Hence, we can say that the major cause of all the weather changes and winds is due to the relation between the Sun and the Earth.