The urban heat-island effect occurs as a result of increased sensible heat flux from the land surface to the atmosphere near cities. Sensible heat flux consists of two components: exhausted anthropogenic heat, and heat radiation due to solar input. The latter may be enhanced by changes in the usage of artificial land surface. The authors have developed a new method to separate the anthropogenically discharged heat and natural heat radiation from the sensible heat flux, based on a heat-balance model using satellite remote sensing and ground meteorological data. This method was applied to ASTER and ETM+ data for the daytime during spring, summer and winter and for the nighttime during autumn in Nagoya, Japan. The increased sensible heat flux was approximately 100 W/m2 in the central part of the city during the summer. Sensible heat flux at night during autumn was approximately 0 W/m2, except in urban areas and over bodies of water. During the winter, anthropogenic heat accounted for almost all of the sensible heat flux in urban areas. The contribution of anthropogenic heat to sensible heat flux in spring was lower than the contributions in summer and winter. The anthropogenic heat flux was high in industrial areas throughout the year. These results are consistent with the fact that anthropogenic energy consumption is high in summer and winter and low in spring and autumn.