Weather forecasting is the application of science and technology to predict the state of the atmosphere for a future time and a given location.
Human beings have attempted to predict the weather since time immemorial. Today, weather forecasts are made by collecting quantitative data about the current state of the atmosphere and using scientific understanding of atmospheric processes to project how the atmosphere will evolve. The chaotic nature of the atmosphere, the massive computational power required to solve the equations that describe the atmosphere, and incomplete understanding of atmospheric processes mean that forecasts become less accurate as the difference in time between the present moment and the time for which the forcast is being made (the range of the forecast) increases.