The urban heat island (UHI) intensity in Beijing, China, has been investigated using temperature data measure at 20 observation stations from 1971 to 2000. The impact of urban growth on the heat island also has been studied by statistic analyzing economic and social development of Beijing. Three urban stations and seven suburb stations were chosen to investigate diurnal and long-term variation of the urban heat island. The conclusion can be drawn as following: (1) The UHI intensity and the total Population logarithm of Beijing are creditable correlated, and the long-term correlative coefficient reaches to 0.76. (2) The urban expansion ( construction cover) is very obvious in Beijing, and the scope of the UHI is spreading simultaneously. (3) The increasing trend of UHI intensity is also found in Beijing. It shows that the UHI has been intensified at a ratio of 0.22 degrees C per 10 years. In 1999, the nightly UHI intensity reached the maximum, 1.13 degrees C. (4) Similar to previous studies for other cities, the maximum UHI intensity is more frequently observed in the nighttime than in the daytime, and it is generally more than 0.5 degrees C. (5) The seasonal trend of UHI intensity is similar for different times (02:00, 08:00, 14:00 and 20:00) of a day. The maximum intensity appears at the nighttime at 02:00 and the minimum at noon at 14:00.
