As cold air falls, it begins to heat up.  Cold air falling is heated by the earth.  When the air is warm, it gets lighter and begins to rise through the atmosphere.  When warm air rises it begins to cool down.  The air then gets heavier and begins to fall.  This cycle is endless and it creates WINDS.  See Diagram

Air always moves from regions of high pressure to low pressure

When air is cooled, it contracts, gets heavier and falls downwards. 

Cold air falling is called DESCENDING AIR.

Descending air increases pressure on the earth’s surface.

Therefore cold air creates HIGH PRESSURE on the earth.

High Pressure usually brings good weather – light gentle breezes, no rain, few clouds and sunny skies.  WHY? But in winter High Pressure can bring frost and ice.  WHY?

When air is heated it expands, gets lighter and rises upwards.

Warm air rising is called ASCENDING AIR.

Ascending air reduces pressure on the earth’s surface.

Therefore warm air results in LOW PRESSURE on the earth’s surface.

Low Pressure brings poor weather conditions – buckets of rain, strong nasty winds, and dark foreboding clouds. WHY?