Weather

Weather refers to the day-to-day state of the atmosphere at a location, including temperature, humidity, precipitation, wind, cloud cover, visibility, and atmospheric pressure. It differs from climate, which describes long-term patterns and averages over years or decades.

Weather arises from energy from the sun, interactions of air and moisture, and heat exchange with oceans, land, and ice. The atmosphere contains features such as high and low pressure systems, fronts, clouds, and jet streams, organized by the Coriolis effect of Earth's rotation. Local geography modulates weather through mountains, coastlines, and urban areas.

Meteorology uses observations from weather stations, radiosondes, radar, satellites, and ships to monitor current conditions. Numerical weather prediction models simulate atmospheric physics to forecast future states. Forecasts rely on data assimilation and ensemble methods, with accuracy generally decreasing with time; probabilistic forecasts and warnings communicate uncertainty.

Common weather phenomena include clouds, rain, snow, sleet, hail, fog, thunderstorms, and hurricanes. Weather affects agriculture, transportation, energy use, and daily activities, and can pose hazards such as floods, droughts, heat waves, tornadoes, and blizzards.

Understanding weather is a foundation of meteorology and climate science. Long-term climate trends can influence the frequency and intensity of some weather events, while natural variability continues to produce significant fluctuations on shorter timescales.