Abstract: A method and system are provided for medium-range probabilistic prediction of extreme temperature events. Extreme temperatures are measured according to how local temperature thresholds are exceeded on daily timescales to generate a local “Magnitude Index” (MI). A regional MI reflecting the historic temperature intensity, duration and spatial extent of extreme temperature events over all locations within the region is then computed. The regional MI is used to create a synoptic catalog for each of one or more pre-defined weather variables by testing the significance of leading modes in historic atmospheric variability across specified periods of time. Current or recent weather conditions are compared against the synoptic catalog to generate probabilistic predictions of extreme temperature events based the presence of synoptic precursors identified in historic patterns.