prediction of the day-to-day atmospheric conditions for a place or area

A weather forecast is a deterministic or probabilistic forecast of the state of the atmosphere with lead-time of an hour up through 10 days. Because of the chaotic nature of the atmosphere no skillful prediction of the exact state of the atmosphere can be made with lead-time of more than two weeks.

A computer generated "best guess" as to what the weather will be at a particular time in a particular area. weather report - A report of the state of the atmosphere at a specific time and with respect to its effect on life and human activities. It is the short term variations of the atmosphere, as opposed to the long term, or climatic, changes. It is often referred to in terms of brightness, cloudiness, humidity, precipitation, temperature, visibility, and wind.