Uncertainties in the hydrometeorological forecasting chain derive from a large number of sources and are inherent to any system. One source of uncertainty is the discrepancy between the meteorological forecasts and the weather which subsequently occurs. Post-processing meteorological forecasts can reduce this discrepancy by removing systematic errors and produce more reliable, corrected forecasts. However, when the corrected NWP output is used in hydrological applications, problems may occur where consistency and correlation between meteorological variables have not been maintained. Therefore a correction that improves the forecast performance of one or more NWP outputs does not necessarily have a positive influence on the hydrological model forecasts. In this chapter the most important needs of the hydrological community in terms of meteorological post-processing are presented. The most commonly used techniques for post-processing are presented along with the pros, cons, and pitfalls in terms of their usage in hydrological applications. Finally, a few important areas of future research are identified.