Weather

Weather is the state of the atmosphere at a specific place at a specific time. Most weather phenomena occur at the lowest level of the atmosphere, also known as the troposphere. Weather refers to the day to day changes in the temperature, precipitation, humidity, winds, pressure, etc.

Causes
There are multiple causes for weather. The main cause is differences in pressure and temperature. This is known as stability. The more unstable the air is, the more thunderstorms and severe weather will occur. Another reason is a low pressure. This is what causes most bad weather situations, including tropical cyclones. An area of high pressure is what usually causes calm winds, and clear skies, and can be accompanied by very warm or cold and dry air.