Introduction: Global warming is resulting in an increase in temperatures which is set to become more marked by the end of the century and depends on the accelerating pace of greenhouse gas emissions into the atmosphere. Yet even in this scenario, so-called “cold waves” will continue to be generated and have an impact on health. Objectives: This study sought to analyse the impact of cold waves on daily mortality at a provincial level in Spain over the 2021–2050 and 2051–2100 time horizons under RCP4.5 and RCP 8.5 emission scenarios, on the basis of two hypotheses: (1) that the cold-wave definition temperature (T threshold) would not vary over time; and, (2) that there would be a variation in T threshold. Material and methods: The results of a retrospective study undertaken for Spain as a whole across the period 2000–2009 enabled us to ascertain the cold-wave definition temperature at a provincial level and its impact on health, measured by reference to population attributable risk (PAR). The minimum daily temperatures projected for each provincial capital considering the above time horizons and emission scenarios were provided by the State Meteorological Agency. On the basis of the T threshold definition values and minimum daily temperatures projected for each province, we calculated the expected impact of low temperatures on mortality under the above two hypotheses. Keeping the PAR values constant, it was assumed that the mortality rate would vary in accordance with the available data. Results: If T threshold remained constant over the above time horizons under both emission scenarios, there would be no cold-related mortality. If T threshold were assumed to vary over time, however, then cold-related mortality would not disappear: it would instead remain practically constant over time and give rise to an estimated overall figure of around 250 deaths per year, equivalent to close on a quarter of Spain’s current annual cold-related mortality and entailing a cost of approximately €1000 million per year. Conclusion: Given that cold waves are not going to disappear and that their impact on mortality is far from negligible and is likely to remain so, public health prevention measures must be implemented to minimise these effects as far as possible.