Heating by the Sun

Heating a surface from directly overhead is more effective than heating a surface at a different angle. When rays of light hit a surface face-on, they are less spread out than if they hit at an angle. At a place on Earth, the heating effect of the Sun is greatest at midday and lowest at sunrise and sunset. Over a day, Earth's spin changes the Sun's height in the sky and the angle at which the Sun's rays arrive at a place.