A traditional approach for studying the urban heat island problem is to investigate the characteristics of the local land use. However, the analysis of the recorded air temperature in the summer in the Great Tokyo, included Tokyo and the sub-urban area of Saitama, Chiba and Kanagawa revealed a picture which is different from the characteristics of the local land use. Saitama prefecture, where a vast area of farm land exists is hotter than the center of Tokyo. Analyze recorded air temperature and wind velocity as well as results of a numerical model indicated that summer monsoon transports hot air from the center of Tokyo to Saitama, contributing to the local heating processes and make Saitama the center of the urban heat island in the Greater Tokyo. Thus it was concluded that future planning of cities needs not only investigating the local land use but also the heating characteristics of the surrouding regions and the heat transport by the local wind.