evidence: Global temperature increases are most clearly detected in the shifting distribution of extreme events. 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. Here, we present the longest historical analysis of daily Australian temperature extremes and their societal impacts compiled to date. 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 daily temperature extremes back to 1838. We identify multidecadal variability in heatwave and snow event frequency with a peak in the early twentieth century, with an overall decrease in cold extremes and an increase in heatwaves in the region over the 1838–2019 period. Documentary and instrumental records show a decrease in the number of snow events in Adelaide, and a clear increase in the number of heatwaves since the late twentieth century. [...] CSIRO and Bureau of Meteorology (2015) Climate change in Australia information for Australia’s Natural Resource Management Regions: Technical Report. CSIRO and Bureau of Meteorology, Melbourne [...] Gergis J, Neukom R, Gallant AJE, Karoly DJ (2016) Australasian temperature reconstruction ensembles spanning the last millennium. J Clim 29:5365–5392