In order to investigate the mitigating effect of the thermal environment in the vicinity of the river and clarify thermal environment of urban area, the authors performed field observations in areas focusing on the Meguro and Arakawa River. From the results of field observation, following results are obtained; 1) There are two classes of air temperature distribution in the vicinity of the Meguro river based on the airy wind direction. 2) The air temperature above the Meguro River shows the lowest among of the observed lines. The maximum air temperature difference is 2 degrees and mitigating effect of thermal environments reaches about 70m from the river. 3) The maximum air temperature difference between the Arakawa river and surrounding areas is 5 degrees.
