This study investigates the urban heat island effect in Singapore and examines the key factors causing this effect. The possibilities of improving heat extraction rate by optimizing air flow in selected hot spots were explored. The effect of building geometry, facade materials and the location of air-conditioning condensers on the outdoor air temperature was explored using computational fluid dynamics (CFD) simulations. It was found that at very low wind speeds, the effect of facade materials and their colours was very significant and the temperature at the middle of a narrow canyon increased up to 2.5 degrees C with the facade material having lower albedo. It was also found that strategically placing a few high-rise towers will enhance the air flow inside the canyon thereby reducing the air temperature. Adopting an optimum HI W ratio for the canyons increased the velocity by up to 35% and reduced the corresponding temperature by up to 0.7 degrees C. (C) 2008 Elsevier Ltd. All rights reserved.