Low pressure systems are usually associated with clouds and rain. Air rotates counter clockwise around and into the low pressure center. In general, as the air moves closer to the center of the system it rises and cools causing water vapor to condense and form clouds and possibly precipitation.

High pressure systems usually bring clear skies with occasional clouds (seldom is there any precipitation). Air rotates clockwise around and away from the high pressure center. As surface air moves away from the high pressure center, air from aloft sinks downward preventing clouds and precipitation from forming.