There has been increasing recognition that climate change may lead to risk of summertime overheating in UK dwellings with potentially adverse consequences for human comfort and health. This paper investigates the magnitude of summertime overheating over one month in 2017, in four new flats built to identical thermal standards, with similar occupancy patterns and located in the same block in a development in Southeast England. Both static and adaptive methods were used to assess the overheating risk, while the variation in indoor temperatures across the flats was examined through key building characteristics including floor level, glazing orientation, exposed surface area to floor area ratio (SA/FA), glazing area to floor area ratio, and ventilation. Data collection included continuous monitoring of indoor and outdoor temperature, relative humidity, CO2 levels and opening/closing of windows. Summertime overheating was found to be prevalent in all four flats but was most pronounced in two top floor flats with high SA/FA ratio and east/west facing glazing. Due to limited window opening and locational limitations of one flat, some conclusions were derived from three flats. Though the study sample is small, it is clear that overheating in new housing is a current issue and designing for avoidance of summertime overheating should become mainstream.