Based on the intensive observation data, the spatial distribution and temporal evolution characteristics of the thermal environment in the main urban area of Hangzhou are revealed. The results show that the effect of urban heat island is the strongest in autumn and winter, the weaker in spring, and the weakest in summer. The most parts of Jianggan, Xiaoshan and Shangcheng are the main highvalue areas of heat island intensity with the annual average more than 0.50 ℃. The peak value can achieve 0.75 ℃ and above in autumn, and over 0.50 ℃ in the other seasons. The high value zone is the largest in winter and the smallest in summer, and the urban heat island effect in Hangzhou tends to expand from the old city to the new city. The urban heat island effect in Hangzhou is strong at night and weak during the daytime with the heat island intensity more than 1.00 ℃ in the high value center at 02:00, then down to 0.50 to 0.75 ℃ at 08:00. The whole city are almost 0.00 to 0.25 ℃ at 14:00, and the maximum reaches more than 0.75 ℃ at 20:00. It is more likely to be muggy in the urban area than in the suburbs, to a greater degree, but the disparity between urban and rural areas has been narrowing in recent years.