The country level percentage of mortality attributable to non- optimum temperature  has been found to range from 3.4 to 11% . Heat as a health risk factor has largely been overlooked in low- and middle- income countries . For 2019, the GBD report estimates the burden of DALYs attributable to low temperature was 2.2 times greater than the burden attributable to high temperature. However, this global figure obscures important regional variations. Countries with a high sociodemographic index-mainly mid-latitude high-income temperate to cool climate countries- were found to have a cold- related burden 15.4 times greater than the heat-related burden, while for warm lower-income regions, such as south Asia and sub-Saharan Africa, the heat-related burden was estimated to be 1.7 times and 3.6 times greater, respectively . For countries where data availability permits, there is evidence that extreme heat  leads to higher rates of premature deaths .
IPCC
Climate Change 2022: Impacts, Adaptation and Vulnerability
IPCC Report