The Heat adaptation priority index (HAPI): A practical tool for urban heat risk assessment and mitigation priority

Urban heat is a growing challenge due to climate change and rapid urbanisation, particularly in hot arid regions like Egypt. The Urban Heat Island (UHI) effect worsens this issue, making densely populated areas significantly warmer than rural ones. This study introduces the Heat Adaptation Priority Index (HAPI), a novel tool for assessing urban heat risk and guiding adaptation policies. HAPI categorises heat risk into seven priority levels to support mitigation planning. The study compares Assiut City, a historic urban center with dense populations and limited greenery, to New Assiut City, a planned city established in 2000 with climate-resilient features in mind. Using Landsat 8 imagery, Land Surface Temperature (LST) and Normalized Difference Vegetation Index (NDVI) were analysed for 2013, 2018, and 2023, alongside Land Use Land Cover (LULC) classification. HAPI integrates LST, NDVI, and proximity to water bodies and agricultural lands retrieved from LULC classification to provide a comprehensive heat adaptation assessment. Results show that New Assiut City remains highly vulnerable to heat stress, with over 92 % of its area classified as a critical priority zone in 2023, highlighting the need for stronger mitigation measures. In contrast, Assiut City exhibits a more varied heat risk distribution, with critical zones ranging from 20.65 % to 28.01 %, while 18.87 % of the city experiences relatively low priority conditions. This study demonstrates HAPI's potential to inform urban policy and support heat adaptation strategies, contributing to sustainable and climate-resilient urban development.