Evolution of the Urban Heat Island in İstanbul from 1965 to 2023: Trends, Migration, and Climate

İstanbul is located in the northwest of Türkiye and is the largest city in the country by population, with an estimated 16 million inhabitants. It also serves as the country's principal economic hub. Consequently, the city is experiencing significant migration both from other regions within Türkiye and from abroad. Moreover, urbanization in İstanbul is accelerating, driven in part by the increasing influx of refugees. As urbanization and population growth continue, the Urban Heat Island (UHI) effect has significantly intensified, leading to increased precipitation and more frequent heat waves. To investigate this phenomenon, a set of criteria was applied to select meteorological stations from the 44 stations across Istanbul. Six stations were chosen for analysis: Florya, Kireçburnu, Kumköy, Şile, Göztepe, and Kumköy station. These stations were selected to represent urban and rural environments, allowing for a comparative analysis of UHI. The temperature differences between urban and rural stations were analyzed to investigate the UHI effect. A non-parametric Mann-Kendall test was conducted to assess long-term trends in temperature data from these stations, covering the period from 1965 to 2023. For Florya, an urban station in Istanbul, the lowest recorded temperature was 10.18 °C in 1965, which increased to 11.4 °C in 2006, and further rose to 13.51 °C in 2023. In contrast, for Şile, a rural station, the lowest temperature was 10.19 °C in 1965, rising to 10.34 °C in 2006, and increasing substantially to 12.16 °C in 2023. The Mann-Kendall test for the period between 1965 and 2023 indicated a significant upward trend, with a critical value of 1.96 for the 95% confidence level. These results suggest that temperature increases in both urban and rural areas are statistically significant, with both Florya and Şile stations showing a significant increase in temperature during the mid to late 1990s. This study will continue by investigating each station using Mann-Kendall statistical analyses and examining the UHI effect. By summarizing these findings across all sections, the study will also contribute to understanding the potential climate cooling effects associated with UHI migration measures. Keywords: Urban Heat Island; Climate Change; İstanbul; Urbanization; Refugee Influx; Mann-Kendall Test