After carefully analyzing of high temperature in July from 11 stations in Shanghai in the past 10 years, it is founded: (1) July 2003 is the hottest in recent 30 years with the maximum temperatures breaking the 30-years record both in urban and rural areas but the Intensity of Heat Island Effect (IHIE) was not the highest compared with the records of the past 30 years. (2) The suburban average maximum temperature changed slightly in the past 10 years while the average maximum temperature in the urban area went up distinctly. It indicates that the heat island effect resulted from environment exchanges is the main cause of the recent urban temperature increase. (3) The inter-annual variation of IHIE has a rapid period and a smooth period, which was caused by various human activities. The change of IHIE has a positive correlation with the regional temperature fluctuation. (4) IHIE in Shanghai will still increase slowly in the coming years, but if the Shanghai Municipal Government has a reasonable city development plan, the temperature increase will be slow down gradually, and IHIE in Shanghai will become stable finally.