Weather is that the state of the atmosphere, describing, for instance, the degree to which it's hot or cold, wet or dry, calm or stormy, clear or cloudy. Most weather phenomena occur within the lowest level of the atmosphere, the troposphere, slightly below the stratosphere. Weather refers to day-to-day temperature and precipitation activity, whereas climate is that the term for the averaging of atmospheric conditions over longer periods of your time. When used without qualification, "weather" is usually understood to mean the weather of Earth.

Weather is driven by atmospheric pressure , temperature and moisture differences between one place and another. These differences can occur thanks to the sun's angle at any particular spot, which varies with latitude. The strong temperature contrast between polar and tropical air gives rise to the most important scale atmospheric circulations: the Hadley Cell, the Ferrel Cell, the Polar Cell, and therefore the airstream . Weather systems within the mid-latitudes, like extratropical cyclones, are caused by instabilities of the jet streamflow. Because the Earth's axis is tilted relative to its plane , sunlight is incident at different angles at different times of the year. On surface , temperatures usually range ±40 °C (−40 °F to 100 °F) annually. Over thousands of years, changes in Earth's orbit can affect the quantity and distribution of solar power received by the world , thus influencing long-term climate and global global climate change .

Surface temperature differences successively cause pressure differences. Higher altitudes are cooler than lower altitudes, as most atmospheric heating is thanks to contact with the surface while radiative losses to space are mostly constant. meteorology is that the application of science and technology to predict the state of the atmosphere for a future time and a given location. The Earth's weather system may be a chaotic system; as a result, small changes to at least one a part of the system can grow to possess large effects on the system as an entire . Human attempts to regulate the weather have occurred throughout history, and there's evidence that human activities like agriculture and industry have modified weather patterns.

Studying how the weather works on other planets has been helpful in understanding how weather works on Earth. A famous landmark within the system , Jupiter's Great Red Spot, is an anticyclonic storm known to possess existed for a minimum of 300 years. However, the weather isn't limited to planetary bodies. A star's corona is consistently being lost to space, creating what's essentially a really thin atmosphere throughout the system . The movement of mass ejected from the Sun is understood because the solar radiation .