In order to understand the types of weather conditions generally associated with high and low pressure systems, we must think “vertically.” The motion of air in the atmosphere above our heads plays a large part in the weather we experience here at earth’s surface. Basically, air cools as it rises, which can cause water vapor in the air to condense into liquid water droplets, sometimes forming clouds and precipitation. On the other hand, sinking air is associated with warming and drying conditions. So the first important point to keep in mind is rising air = moistening, sinking air = drying.