The distribution of overall temperature and the frequency of heat waves may be shifting due to climate change. However, forecasting future health consequences of higher temperatures in a given city is complicated by uncertainties in how populations and societal infrastructure will adapt. This paper reviews approaches to address these challenges, including: (1) using historical weather–mortality relationships for the same region, or a location with a similar climate as the city of interest; (2) evaluating adaptation using the minimum mortality threshold (MMT) temperature (i.e., the temperature with the lowest mortality rate); and (3) estimating the impact of modifiers (e.g., air conditioning, population density, green space) on the temperature and mortality relation, and then predicting a range of effects based on plausible estimates for the future values of these parameters in a given city. Each approach can provide insight into how heat could affect mortality under a changing climate, but all have uncertainties. In spite of these limitations, projecting the future public health burden of temperature-related health effects can provide valuable information to aid public health and environmental authorities in planning and communicating the risks of climate change to the public.