Heat-related mortality tends to be associated with heatwaves that do not allow for sufficient acclimatisation to hot weather. 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 forecasts of heat-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 combined with projections of temperature from three major Global Climate Models to develop forecasts of heat-related mortality for the period between 2017 and 2041. The estimated thresholds coincide with a notable impact of hot weather on mortality, but a limited cold weather impact. As this is carried over into the forecasts, 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 a recent study that found that cold weather-related mortality within Australian capital cities has and will continue to be notable.