THUNDER AND LIGHTENING

When cold air meets warm air, the cold air sinks and digs under the warm air, forcing it to rise quickly.  The rising air takes water vapor with it, which cools and condenses, forming cumulonimbus clouds, sometimes called thunderheads.  These are deep, dark, tall clouds, formed as  water vapor condenses, releasing heat, pushing the air higher and higher.  No one is sure exactly why lightning occurs, but water droplets and ice particles bang together in the cloud, helping to build up positive and negative electrical charges.  The positive charges gather near the top of the cloud and the negative charges gather in the middle.  More positive charges gather near the bottom of the cloud and on the ground below the cloud.  Electricity flows between the charges.  The flash of electricity is lightning.
   Lightning heats the air around it.  The heat causes the air to expand with an explosive  force, resulting in a loud sonic boom we call thunder.