The main objective of the present study is to investigate the mechanism of triggering slope failures during extreme rainfall events under the climatic and geological conditions of Ha Giang city, Viet Nam. For this purpose, the specific research objectives of this paper were based on the analytic results of the geotechnical properties of the soil samples. The pore water pressure distribution on a slope was changed by the influence of rainfall. In order to analyze the stability of the cut slopes, the two modules SEEP/W and SLOPE/W in the GEOSTUDIO 2012 software were employed and integrated. First, the initial steady seepage condition was used to assess the effect of extreme rainfall for a transient seepage. Second, the soil sample properties and some features were assigned in the slope stability model, such as unit weight, cohesion, internal friction angle, and hydraulic functions, and then the achieved transient pore water pressure regime was used as the input parameter to calculate the factor of safety (FS) on cut slopes. Finally, the relationship between the changing of the FS over time and the hourly rainfall intensity that resulted in slope failure were evaluated. In summary, the slopes in Ha Giang city can be stable under normal conditions, but their stability is always a dilemma for local authorities due to the influence of intense rainfall.