This study aims at clarifying the regional heat balance characteristics in an urban space of a city. CFD analyses of mesoscale climates of Tokyo, Sendai and Haramachi were carried out. The influence of regional characteristics on urban climates was examined, based on the results of CFD analyses, by considering the heat balance mechanism in the central part of each city. It was confirmed that the factors greatly contributing to air temperature increasing and decreasing in each city was different. Furthermore, the spatial distribution of heat budget inside Sendai city was drawn, as “Heat Balance Map”. The map illustrated the areas where influence of sea breeze was significant in contrast with heat generated from ground surfaces and anthropogenic heat release in this city.