The Himalayas comprise one of the largest collections of glaciers outside the polar regions, with glacier coverage of ~33,000 km2 (Dyurgerov and Meier 1997). The rivers of the Himalayas are of glacial origin and are thus perennial. Since the mid of last century many large glaciers in Himalayas have disintegrated to smaller glaciers primarily due to global warming (Kulkarni et al. 2007; Shrestha et al. 2012). During this glacier melt, several glacial lakes form up in the vicinity of retreating glaciers or from their melt water (Jain et al. 2012). These glacial lakes are mostly situated in elevation between 3000-5000 m elevations and are formed in unstable regions. During Glacial lake outburst fl oods (GLOF), they can produce discharge rates of 30,000 m3 sec−1 which can cover over 200 km in downstream region (Richardson 2000). Thus, a detailed approach is required to mark out these potential risky lakes before they begin to get into severe conditions. An extreme rainfall event coupled with them having vulnerable lithology and slopes could trigger a fl ash fl ood event in the area. This study investigates the possibility of a glacial lake outburst fl ood in Sikkim, which has a massive topography and extensive annual precipitation. Based on the analysis of geomorphic, climatic, and tectonic processes in Sikkim, a vulnerable glacial lake were identifi ed.