Rapid urban growth has led to an increase in the density of buildings, asphalt, and concrete, which absorb and retain heat. This causes the formation of urban heat islands; areas where the temperature is higher than the surrounding villages or green areas. The removal of green spaces and the reduction of natural air flow disrupt natural evaporation and cooling. As a result, urban night temperatures increase and energy consumption for cooling and ventilation also increases. The aim of the present study is to investigate the role of urban growth patterns in the creation of heat islands in cities (case study: Arak city). This study is applied-theoretical in terms of purpose and descriptive-analytical in terms of method. The required information and data were collected through library and field methods. The ISM model method was used in this study. The analysis results show that the horizontal and unplanned expansion of the city, land use change, especially the replacement of green areas with impermeable surfaces such as asphalt and concrete, play a key role in increasing the temperature of the earth's surface. Also, the high density of buildings and the lack of natural ventilation have intensified the accumulation of heat in the central areas of the city. The ISM model with its hierarchical structure showed that variables such as land use patterns, the physical development of the city, and the amount of vegetation cover have the most direct impact on the heat island phenomenon. Therefore, optimal management of urban growth through monitoring thermal changes, revitalizing green spaces, and controlling excessive urban development can play a fundamental role in reducing the effects of "heat islands" in the city of Arak.