Australia’s warming climate has resulted in significant changes in the frequency of temperature extremes, with a general increase in heatwaves and a reduction in the number of cold days. This study presents the longest historical analysis to date of daily Australian temperature extremes and their societal impacts. We use a newly consolidated early instrumental dataset and a range of historical sources for the South Australia region of Adelaide— the nation’s driest state, containing the most heatwave-affected city in Australia—to investigate any changes in the characteristics of temperature extremes back to 1838. We examine the frequency and impacts of past heatwaves and cold extremes, with particular emphasis on the lesser-known events of the pre-1910 period and unusual low-elevation snow events. We also present detailed case studies from the pre-1910 period to compare characteristics of historical and contemporary hot and cold extremes and their impacts as recorded in early instrumental and documentary records. Finally, we discuss the value and limitations of using historical instrumental and documentary data to assess long-term changes in Australian temperature extremes and their potential to improve future climate change risk assessment.