WHAT IS ALREADY KNOWN ABOUT THIS TOPIC? In recent years, climate change may lead to an increase in cold spells in the middle latitudes, and there is a positive correlation between cold spells and population mortality. WHAT IS ADDED BY THIS REPORT? The acute response period and the vulnerable population were identified under the optimal definition of cold spells, and the mortality burden caused by cold spells was estimated. WHAT ARE THE IMPLICATIONS FOR PUBLIC HEALTH PRACTICE? This research would provide evidence on the acute mortality effects of cold spells in southern China. Therefore, vulnerable populations, especially the elderly, should take timely measures to reduce the health damage caused by cold spells, especially in the first week after cold waves.