The surface of the earth is heated by the sun rays, and the air is warmed by heat rising from the warm surface. The warmth or heat of the air is called its temperature. Temperature is measured with a thermometer, which is a scale of degrees. some thermometers uses the fahrenheit(F) scale , on which the freezing point of water is 32 degree and the boiling point is 212 degree. Others uses the celsius(C) scale, on which the freezing and boiling points are 0 degree and 100 degree respectively.
The earth gets its heat from the sun. Air is made up mainly of gasses, so the sun rays pass through the atmosphere quiet easily. Not all of the sun heat reaches the earth. some of its reflected back to space and some is absorbed by the clouds. The amount that does reach the surface heats it up. The heated surface warms the air immediately above it.
Hot Air , being light, rises. As it does cool air descends to take it place. The cool Air in turns is heated by the warm surf