Assessing Heat Vulnerability in Toulouse: A Spatiotemporal Approach Using Google Earth Engine ^†

Urban heat vulnerability is a growing concern for public health, particularly in rapidly urbanizing regions. This study presents a case analysis of Toulouse, France, to assess the Heat Vulnerability Index (HVI) by integrating environmental, socioeconomic, and demographic factors. Key environmental indicators such as ground-level ozone, PM₁₀, PM_2.5, land surface temperature (LST), land use/land cover (LULC), Normalized Difference Vegetation Index (NDVI), Normalized Difference Built-up Index (NDBI), and Normalized Difference Water Index (NDWI) were derived using satellite remote sensing data from Google Earth Engine, including Landsat 8 and Sentinel-5P datasets. Socioeconomic and demographic variables, such as population density, elderly residents (65+), socially isolated elders, literacy rates, and poverty levels, were also incorporated. Additionally, mortality data of the city related to urban heat and air quality impacts in recent years were analyzed and it shows that urban heat and air pollution are closely linked, and their combined effects can significantly increase health risks every year, especially in densely populated cities. Temporal HVI maps were generated and analyzed to observe recent years trends, revealing a persistent increase in vulnerability across the city especially in areas with limited vegetation and large expanses of high heat absorptive building and pavements materials. These findings highlight the urgent need for targeted mitigation strategies to improve public health, strengthen urban resilience, and enhance overall human well-being. Particularly by guiding urban planners and municipalities in designing greener, more heat-resilient environments.