Urban heat island (UHI) phenomenon has become a common problem in many major cities worldwide including Singapore. As a small island state, it is very important for Singapore to carefully plan its urban development. However, urban planners have no assessment tool to evaluate their planning impacts on the environment, especially the impact on air temperature due to the change of land use. This paper discusses the development of an empirical model for air temperature prediction to evaluate the impact of estate development by means of Geographical Information System (GIS). Empirical models of minimum (Tmin), average (Tavg) and maximum (Tmax) air temperature for Singapore estate have been developed and validated, based on the long-term field measurement between the period of September 2005 and March 2008. The independent variables that were used in the models are daily minimum (Ref Tmin), average (Ref Tavg) and maximum (Ref Tmax) temperature at reference point, average of daily solar radiation (SOLAR), percentage of pavement area over R 50m surface area (PAVE), average height to building area ratio (HBDG), total wall surface area (WALL), Green Plot Ratio (GnPR), sky view factor (SVF) and average surface albedo (ALB). Sensitivity analyses were carried out to observe the dependence of the air temperature due to the variations of each variable. An ideal type of urban canyon was used to simplify the variation of building, pavement and greenery distributions. The sensitivity analyses were carried out by varying some of the following important parameters: the greenery density (GnPR), which may affect the SVF; the building height, which affects the SVF, WALL and HBDG values; and canyon width, which affects the SVF, PAVE AND HBDG values. The Screening Tool for Estate Environment Evaluation (STEVE) was developed with the motivation to bridge between research findings, especially the air temperature prediction models and the urban planners.