In the Indian Himalayas, slope instability remains a recurrent natural hazard, increasingly aggravated by the intensification of rainfall events linked to climate change. The growing frequency of extreme precipitation has amplified pore-water pressures and infiltration-induced failures, making it essential to evaluate slope stability under changing climatic conditions. This study employs numerical modelling approaches to assess the Factor of Safety (FOS) by considering the combined effects of soil properties, slope geometry, and rainfall infiltration. A detailed case study was conducted in Kalimpong, a highly landslide-prone region, focusing on a slope near Happy Villa that experienced rainfall-triggered failure. The analysis utilized SLOPE/W (Limit Equilibrium Method) and PLAXIS 2D (Finite Element Method) software to evaluate slope performance under unsaturated and saturated conditions, representing pre- and post-rainfall scenarios. In the limit equilibrium method, FOS values were 1.139 (unsaturated) and 0.449 (saturated), while in the finite element method, the corresponding values were 1.13 and 0.39. Both modelling approaches consistently revealed that steep slope gradients combined with rainfall-induced saturation significantly reduce slope stability, confirming rainfall infiltration as a critical triggering mechanism. The results highlight the growing influence of climate-induced hydrological variability on slope behavior and emphasize the need to incorporate climate change considerations into regional landslide hazard assessments and slope management strategies. Proactive adaptation through improved drainage, slope reinforcement, and climate-resilient planning is essential to mitigate future failure risks in Himalayan terrains.