This study aims to estimate the potential of physical characteristics and to combine different type of physical factors that might affect urban heat island effect based on 55 observations in 2016 for Ulsan. The climatic variations in summer were controlled by classifying the data into clear sky, partially cloudy and cloudy period. The geographical variations were controlled by classifying the data into core, urban and semi urban areas. This research uses seven variables, namely surface albedo, green density ratio, sky view factor, sunshine factor, altitude above sea level, distance from city centre, and canyon orientation for regression analysis. Distance and green density ratio are critical variable that determine urban heat island intensity of daytime and nocturnal. The maximum temperature of the daytime for the city centre and rural area in August had a slightly difference but the minimum temperature of nocturnal showed a significant difference. The tropical nights in the city centre of Ulsan occurred at twice more in the Ulsan weather station. It also examined the implications of the effect of the urban heat island available to designers and planners for buildings and urban environment.