The definition and quantification of urban heat island (UHI), the air temperature differences between urban and rural areas, remains problematic. This is due, in large part, to the difficulty of operationalizing the terms “urban” and “rural”, especially with regard to classifying the weather stations that provide data. This thesis studies the urban heat island (UHI) intensity in Hong Kong and there are three foci in the research. The first focus of this study is the determination of the urban and rural weather stations in Hong Kong. The Local Climate Zones (LCZ) system has been employed to classify 17 weather stations and field observation was the main technique to collect the necessary metadata. Six field trips were arranged in the summer of 2009 and 2010. Hong Kong Observatory Headquarters (HKO) is considered as the only representative urban station, whilst Tsak Yue Wu station (TYW) is deemed as the representative rural station because of its Forest Zone (NCZ1) classification. Ta Kwu Ling station (TKL) is another reference rural site. The second focus is the quantification of the UHI intensities at six pairs of stations in Hong Kong and their diurnal and seasonal variations. The 19-year annual UHI intensities in Hong Kong suggest that the representative rural sites (TYW and TKL) also record representative UHI intensities for the region. The differences of the cooling rate at urban and rural stations drive the diurnal cycle of urban heat island. The seasonal variations of UHI intensities are also driven by the cooling rate differences of urban and rural stations in different seasons. Since the mean maximum urban cooling rate does not vary considerably throughout the seasons (0.4 – 0.5 °C/hr), it is the alteration of the rural cooling rate (1.0 – 1.6 °C/hr at TYW; 0.9 – 1.2 °C/hr at TKL) which determines the seasonal variations of UHI intensities. The mean daily maximum UHI intensities in Hong Kong are greatest in winter. The final focus is the meteorological impacts on the UHI intensity in Hong Kong. Five meteorological elements, including air temperature, wind speed, vapour pressure, cloud cover, and cooling rate, have been separately investigated to establish their impacts on the UHI intensity. Under fine weather conditions, the first four elements are negatively related to the UHI intensity. Sixteen regression models were built after the use of stepwise procedures which optimize the combination of independent variables. Rural air temperature is considered the most important meteorological factor on the UHI intensity. The models also suggest that there are other factors affecting the UHI intensities in spring and summer.