Climate diagnostic archives appears to be a very useful tool for astronomical site assessment. These climatological databases combine data from meteorological archives for different data sources (radiosoundings, satellites, etc) and meteorological models to derived any parameter at a particular selected location. Although the products from climate diagnostic archives are heavily constrained by observational data, a rigorous control of data quality, analysis and cross comparison needs to be performed before the method becomes extensively used for site characterisation. In this talk we present an statistical analysis of winds, an important parameter for site characterisation, using in-situ measurements (ground level and balloon data) and data derive from climate diagnostic archives. The cross-comparison of results obtained from the two set of data allow us to propose some restrictions in the use of climate diagnostic products for site characterisation.