In this study, the frequency of occurrence of cold water masses along the east coast of Korea was analyzed using long-term data on water temperature and current velocity, and the correlation between the occurrence of cold water masses and the variability of the path of the East Korean Warm Current (EKWC) moving northward along the coast was investigated. The highest frequency of cold-water masses in August was found in Ulgi (45 %), followed by Gampo (33%) and Busan (22%) in the southern East Sea region. The EKWC, which flows northward along the southern East Sea coast, showed route variations as it passed 36.5°N. The primary route variations of the EKWC can be divided into three patterns. The first is when the EKWC flows northward near the coast (on-coastal); the second is when it flows northward along the 129.7°E line, approximately 40 km from the Hupo coast (normal); and the third is when the current moves northward along a path far from the coast (off-coastal). The probability of a cold-water mass occurring at the Ulgi coast for each of these three EKWC route variations was 22% when the current flowed northward near the coast (on-coastal), 0% when it flowed northward without route variation (normal), and 91% when it moved northward offshore (off-coastal). In addition, an analysis of the flow characteristics at each point along the Hupo line (H-01 to H-10) and their contribution to water temperature at the Ulgi coast showed that changes in the EKWC path along the Hupo coast contributed significantly to the occurrence of cold-water masses along the Ulgi coast. The Coherence current velocity in the Hupo coastal area (H-01 to H-03) and Ulgi water temperature were greater than 0.7, whereas they were less than 0.5, in the offshore areas (H-06 to H-10). Therefore, the occurrence of cold-water masses on the Ulgi coast is highly correlated with variations in the EKWC flow on the Hupo coast.