Vegetation’s role on temperature regulation has been commonly recognized, but its relationship with Leaf Area Index(LAI) and trees’ specie have not been studied. During November–December, 2007, air temperature were recorded at Faculty of Science, Mahidol University(SC) which has green area as 24% of total area and average LAI is 2.92 unit, compared with Rajvithi Home for Girls (RJ) that located nearby with 8% of plant-cover and value of average LAI is 1.12. Average temperature during study period is 33.1 and 35.0 °C at SC and RJ, respectively. Regression analysis shows that when one unit of LAI increase, maximum temperature is 0.16 °C lower at SC ( p 0.05). Planting trees thus should consider not only decorative values but high LAI to help regulating local temperature of an area.