In Singapore, rapid population influx has led to demands for converting natural areas to pubic housing. The heat island in Singapore city has been documented. However, less attention has been placed on the cooling effect of city's green areas. To address this issue, temperature and humidity measurements were conducted in two big city green areas. One is the city's natural reserve-Bukit Batok Nature Park (BBNP) (36 ha) and the other is a neighbourhood park-Clementi Woods Park (CWP) (12 ha). The measurements were conducted at both vegetated areas and their surroundings. The results indicated the cooling effects of city greens are remarkable not only at vegetated areas but also the surrounding built environments. To further explore the role of the green area on moderating the microclimate, two simulation programmes, TAS and Envi-met, were employed, respectively, for the two parks. The aims are to explore the patterns of energy consumptions of a typical commercial building near to Bukit Batok Nature Park and different thermal conditions with and without Clementi Woods. (c) 2005 Elsevier B.V. All rights reserved.