Weather - The state of the atmosphere at a particular place during a short period of time. It involves such atmospheric phenomena as temperature, humidity, precipitation (type and amount), air pressure, wind, and cloud cover. Weather differs from climate in that the latter includes the synthesis of weather conditions that have prevailed over a given area during a long time period—generally 30 years. For a full discussion of the elements and origins of weather, see climate. For a treatment of how conditions in space affect satellites and other technologies, see space weather.