The aims of this study are to assess the impacts of accelerated climate change on summer maximum temperatures since the early 1990s in the Australian city of Sydney’s eastern coastal and western inland suburbs. Western Sydney currently experiences far more intense summer (December–March) heat waves than coastal Sydney, with maximum temperatures exceeding those of coastal Sydney by up to 10 °C. Aside from increased bushfire danger, extreme temperature days pose health and socio-economic threats to western Sydney. Permutation tests of consecutive summer periods, 1962–1991 and 1992–2021, are employed to determine the differential climate change impacts on maximum summer temperatures at two locations: Sydney and Richmond, representative of eastern and western Sydney, respectively. Attribution of observed maximum summer temperature trends in Sydney and Richmond was performed using machine learning techniques applied to known Australian region oceanic and atmospheric climate drivers. It was found that there is a marked disparity in the percentage of summer days above the 95th percentile during the accelerated climate change period (1992–2021) between Richmond (+35%) and Sydney (−24%), relative to 1962–1991. The climate drivers detected as attributes were similar in both Sydney and Richmond, but, unsurprisingly, Sydney was more affected than Richmond by the oceanic climate drivers.