ETYM Old Eng. weder, AS. weder.
(Homonym: wether, whether).
The meteorological conditions: temperature and wind and clouds and precipitation; SYN. weather condition, atmospheric condition.
Day-to-day variation of climatic and atmospheric conditions at any one place, or the state of these conditions at a place at any one time. Such conditions include humidity, precipitation, temperature, cloud cover, visibility, and wind. To a meteorologist the term “weather” is limited to the state of the sky, precipitation, and visibility as affected by fog or mist. A region’s climate is derived from the average weather conditions over a long period of time. See also meteorology.
Weather forecasts, in which the likely weather is predicted for a particular area, based on meteorological readings, may be short-range (covering a period of one or two days), medium-range (five to seven days), or long-range (a month or so). Readings from a series of scattered recording stations are collected and compiled on a weather map. Such a procedure is called synoptic forecasting. The weather map uses conventional symbols to show the state of the sky, the wind speed and direction, the kind of precipitation, and other details at each gathering station. Points of equal atmospheric pressure are joined by lines called isobars. The trends shown on such a map can be extrapolated to predict what weather is coming.