Outdoor thermal comfort in hot arid and semi-arid cities of the Middle East and North Africa: current knowledge, gaps, and a framework for climate-sensitive urban design

Introduction Outdoor thermal comfort (OTC) has become a critical determinant of urban livability, public health, and energy demand in cities exposed to escalating heat stress. In hot arid and semi-arid MENA contexts, extreme solar radiation, high mean radiant temperature, and rapid urbanization intensify thermal discomfort in outdoor spaces. Despite growing research interest, OTC knowledge in the region remains fragmented, methodologically inconsistent, and weakly contextualized. Methods This review provides the first region-specific, integrated synthesis of OTC research across hot arid and semi-arid MENA cities, covering Egypt, the Gulf Cooperation Council (GCC) states, the Levant, and North Africa. Using a PRISMA-guided methodology, 120 peer-reviewed studies published between 2010 and 2025 were systematically classified and analysed according to geographic coverage, methodological approach, spatial scale, thermal indices, urban morphology parameters, microclimate modifiers, and human adaptation dimensions. Results The review reveals five persistent gaps: (i) strong geographic and climatic concentration of studies with limited regional integration; (ii) widespread application of thermal indices (PET and UTCI) without calibration for extreme radiant environments; (iii) dominance of micro-scale, site-specific analyses with limited neighbourhood- and city-scale integration; (iv) underrepresentation of behavioural and cultural adaptation despite robust empirical evidence; and (v) minimal consideration of advanced façade and shading technologies widely implemented in MENA cities. Discussion Synthesising evidence across physical, behavioural, and technological domains, the paper proposes an integrated conceptual framework positioning urban morphology as the primary mediator between climatic forcing, microclimate modification, thermal indices, and human perception. The framework explicitly incorporates radiative control mechanisms, seasonal sensitivity, behavioural adaptation, and multi-scale feedbacks. By consolidating fragmented evidence into a regionally grounded framework, this review advances OTC theory and provides actionable guidance for climate-responsive urban design, modelling, and policy development in hot arid and semi-arid cities.