The Urban Heat Island: Increasing Temperature Trends in Central European Cities (Vienna, Rome & Zagreb)

Abstract

This study uses Landsat 8/9 images to quantify the Land Surface Temperature (LST) and urban-rural comparisons to assess Urban Heat Islands (UHIs) and seasonal warming trends in Vienna (Austria), Rome (Italy), and Zagreb (Croatia). We analyzed monthly LST patterns and Surface Urban Heat Index (SUHI) of 2024 for each city and seasonal temperature trends (2014-2025) in February and July for Zagreb and Rome. Additionally, we computed the intra-urban k-means clustering of 2024 based on the mean temperatures of these cities into three different zones (Zone 1: Cool Cluster, Zone 2: Average Mean Temperature Units & Zone 3: Hot Cluster). In all three study areas, the urban zones dominantly show higher temperatures in comparison with their respective rural surroundings with positive SUHI. The strongest SUHI observed was +6.63 °C in Rome in spring 2024. Some winter months with negative SUHI (urban zones being cooler than the rural ones) indicate the occasional ‘cool island' effect (Rome had the largest cool island effect (–1.94 °C in winter) at the same time). The seasonal trend analysis of the last decade unleashes an overall warming pattern both in urban and rural zones, with a striking spring warming, consistent with European climate trends.