AUSTIN (KXAN) -- The air around us isn't weightless. In fact, it's pushing down on us at all times, and not just us, but the world around us too. All that pressure plays a big role in whether the weather is sunny or stormy. In this First Warning Weather University lesson, Chief Meteorologist Nick Bannin takes a closer look at pressure systems and the role they play in forecasting the weather. In this FWWU lesson you will learn: How much does air weigh? What do the symbols on a forecaster's map mean? How do different pressure systems influence the weather? More lessons from First Warning Weather University Why do we have seasons? How does humidity influence the temperature? What does a "chance of rain" really mean?