Heavy rainfall can lead to shallow slips on slopes which are often initially in a state of partial water saturation. A multiphysics approach and advanced constitutive modeling are necessary to take into account the physical key processes in partially saturated soils during rainfall events, such as water flow through the solid matrix, soil water retention behavior and the effects of matric suction on the mechanical behavior. The elasto-plastic constitutive model ACMEG-s that includes an elasto-plastic water retention model with wetting-drying hysteresis is used in the framework of finite element modeling for the assessment of destabilizing, transient processes in a steep slope during rain infiltration. It is shown that at the onset of failure, wetting pore collapse and plastic shear strains occur in the lower part of the slope and develop upwards towards the slope surface to delimit a probable failure mechanism.