In this paper the set-up of a fully functional landslide warning system, based on rainfall thresholds, is described. This work was developed in Tuscany region (Italy), an area characterized by a heterogeneous distribution of relieves and rainfalls. The work started with the initial definition of a single set of rainfall thresholds, but it resulted to be ineffective to EWS purposes. Then a software capable to analyze several rainfall events in short time was developed, in order to overcome the problem of the subjectivity of the analyses. Once the thresholds were defined, a WebGis-based warning system was developed. This system can use both real time and forecasting rainfall data and identifies the most hazardous rainfall of each rain event. The last step of this work was the updating of the thresholds using an enhanced calibration dataset, to enhance the performances of the EWS and to account for the changes on territory and on rainfall distribution.