Extreme weather events, such as heat waves, are expected to become more frequent and more intense as a consequence of global climate change affecting the health and well-being of the population even in regions with moderate climates, such as Central Europe. Utilizing spatiotemporal meteorological data and an exhaustive administrative database on all hospital admissions from 2009 to 2019 in the metropolitan area of Vienna, we model the relationship between thermal hazards and hospitalisations. Differentiation by age, gender, socioeconomic status and degree of urbanization, allows to account for demographic dynamics and agglomeration effects when projecting the future burden of urban heat on health and healthcare. To the best of our knowledge, no other study so far considers climate effects on health in conjunction with the differential vulnerability of the exposed population in the urban environment.