The problem of creeping landslides accompanied by heat production due to friction on their base is studied here. The landslide is modelled using a rigid block that slides over a clayey zone of finite width and a thermal softening and velocity strengthening constitutive law for the friction coefficient of the basal clay material. As time progresses, the sliding process enters an irreversible, highly unstable procedure, when the heat dissipation at the base of the slide starts localizing towards an infinitesimally small shear band of the order of mm. The influence of this transition to the stability of the slide is explored by applying this model in the famous landslide of the Vaiont valley (Northern Italy). The model is calibrated upon the real velocity data of the slide verifying that the onset of the localization of dissipation is also a stability threshold for deep seated thermally driven landslides. © 2010 Taylor & Francis Group, LLC.