Heat-related mortality tends to be associated with heatwaves that do not allow for sufficient acclimatisation to hot temperatures. In contrast, damage functions and most heatwave emergency response plans do not account for acclimatisation. Using an excess heat measure that accounts for acclimatisation, this paper produces estimates of temperature-related mortality for the five largest Australian capital cities. Fixed effects panel threshold regressions are applied to establish the thresholds that coincide with heightened mortality during extreme temperature events. The estimated parameters associated with these thresholds are then used to develop hindcast estimates for cold temperatures, moderate temperatures, hot temperatures and extreme heat. The estimated thresholds coincide with a notable impact of hot temperatures on mortality, but a limited cold temperature impact. This shows that the burden of risk associated with mortality related to future temperatures and climate change within Australia coincides with heatwaves rather than coldwaves. This is in contrast to recent studies that found that cold temperature-related mortality within Australian capital cities has and will continue to be notable.