In today’s big cities, it is observed that due to the decrease of green areas due to anthropological interventions, asphalt surfaces and building areas increase, meteorological parameters are changed. Thus, in many metropolises, cities have distinctive climatic characteristics and they cause local and regional climate changes. This climate differentiation between urban areas and rural areas with geographical similarity is called Urban Heat Island. As a result, changes in urban climate and new microclimatic properties and air pollution play a negative role on the health and comfort of people. The aim of this study is to show that the factors such as industrialization, population growth and migration in Mersin have created an urban heat island in the city. In this study, the city center population was selected as Silifke, which is the rural station to be compared in terms of urban heat island with Mersin, which has more than 500.000 inhabitants. The criteria of extreme elevation difference between the two measuring stations which do not affect the climatic parameters, such as the absence of a geographic shape such as lake or high peak were taken into consideration. The annual and seasonal trend analyzes of the 65-year temperature datasets of the General Directorate of Meteorology between 1951 and 2016 were carried out and Sen’s Trend Education method was used to reveal the temperature differences. When the trends are analyzed on an annual basis, Mersin is 4,1 °C warmer than the comparative station Silifke at the minimum temperatures shown by the urban heat island.