A. Weather occurs because the heat of the sun keeps the atmosphere constantly in motion. The position of the sun is what causes temperature changes. When the sun is high in the sky its rays strike the ground directly producing maximum heat. When the sun is low its rays strike at an angle and its heat is spread out over a wider area. C. Heat from the sun changes water from oceans and lakes into an invisible gas called water vapor.
Air masses are enormous bodies of air that form over areas where temperatures are fairly constant.
A. Air masses influence the area weather. Air masses take on the temperature of the area. Cold and warm air masses do not mix rather they form boundaries. They may cover 5 million square miles. B. Four major types of air masses affect the weather as they move above the earth.