Abstract: Based on the air temperature data measured by automatic weather stations in the Kunming area during the period 2004-2012, the diurnal, seasonal, and interannual variation in the urban heat island effect in Kunming, its horizontal distribution, and tendency, were analyzed. The results indicated that the urban heat island intensity (UHI) possessed significant diurnal variation, which was larger at night and became weaker during the daytime. Usually, the UHI reached its maximum at 0800 LST, and became weaker or disappeared at 1400 LST. On the seasonal scale, UHI was largest in winter, followed by spring and autumn, and then summer. The annual average UHI during 2004-2009 was 1.27 ℃, and showed a tendency to decrease in the latter years of the study period due to the increase in cloud. During 2004-2007, the center of the heat island was located in the center of the city, but it seemed to become larger in area and move toward Chenggong and Shilin owing to the rapid growth of the economy and population of medium- and small-sized towns at the county level around Kunming.