The purpose of this study is to examine the regional characteristics on urban climate. CFD analyses of mesoscale climates of Tokyo metropolis, Sendai city and Haramachi city were carried out. All these three cites are faced to the Pacific Ocean but there exit several factors causing the different regional characteristics of urban climates of three cities, i.e. the size of urbanized area, the building density, the conditions of land-use and artificial heat release, etc. The influence of the regional characteristics on the urban climates was examined based on the results of climatic analyses by considering the heat balance in total urban space. In the center parts of Sendai and Haramachi, it was revealed that the effects of sea breeze are very large compared to the effects of artificial heat releases. In the center of Tokyo, the contribution of sea breeze was also large, but the contribution of artificial heat release was also relatively large compared to other two local cities.