This study assesses the impacts of sustainable urban development adapted to climate change in the city of Stuttgart, Germany. We use the state-of-the-art meteorological modelling system PALM-4U to simulate the microclimate and outdoor thermal comfort of the development site Neckarpark during a heatwave. We compare the atmospheric conditions of the current urban structure before the development project (2018) and the future state, representing the new district after completion (2025). Our results indicate that the restructuring barely affects surrounding neighbourhoods, but leads to mean near-surface air temperature increases in the centre of development between [Formula presented] and [Formula presented]. Differences in Physiologically Equivalent Temperature (PET) show a heterogeneous pattern at daytime, with a large amplitude and temporal variability in the diurnal cycle ([Formula presented]). At night, the planned buildings increase the mean PET by [Formula presented]. The new buildings reduce the effect of adaptation measures designed to increase the cooling effects, i.e. urban trees and vegetation, amplifying the thermal stress during heatwaves. Our study confirms the complex composite impacts of urban restructuring due to the thermal and dynamic flow processes. The paper may serve as a guide for the use of meteorological models to assess microclimatic impacts of planned development projects, contributing to urban planning and adaptation strategies.