The temperature of the air generally decreases from the equator toward the poles. 

Because of the spherical shape of the earth the rays of the sun do not fall equally on all parts of the earth, it falls vertically on the equatorial region spreading over a smaller area, and are slanted at the poles, spreading over a larger region. Moreover, as the rays have to travel over a longer distance to reach the polar regions, they lose much of their heat in the process. Therefore, air temperature generally decreases from the equator toward the poles.