Spatiotemporal patterns of excess mortality attributable to prolonged cold spells in China, 2020–2023

While global warming is generally associated with fewer extremely cold days, prolonged cold spells continue to pose important public health concern. However, recent evidence on their spatiotemporal distribution and mortality burden in China is lacking. We conducted a nationwide county-level assessment of prolonged cold spells and their attributable mortality across China from 2020 to 2023. Daily meteorological data were retrieved from the NOAA database, and mortality data from 26 representative cities were analyzed using a time-stratified case-crossover design. Cold spells were defined as ≥ 5 consecutive days with mean temperature below the 5th percentile of the local distribution. Excess deaths were estimated by integrating relative risks with county-level population and crude death rates. During the study period, 11,737 cold spell events were identified nationwide, totaling 94,815 days. The frequency and geographic extent of prolonged cold spells showed notable year-to-year variation, with substantial spatial heterogeneity in their impacts. Overall, 41,614 excess deaths were attributable to prolonged cold spells, and the annual mortality burden fluctuated across the four years, reaching the highest level (16,914 deaths) in 2023. Northern provinces exhibited elevated mortality risks, yet southern provinces such as Chongqing, Sichuan and Guangdong also bore substantial burdens due to large exposed populations. Temporally, excess deaths clustered in December and January, consistent with periods of most severe cold spells. Health risks unequally affected vulnerable groups, particularly women and older adults. Under the background of global warming, prolonged cold spells in China exhibited considerable interannual variability while continuing to impose substantial health burdens nationwide. These findings highlight the need to consider spatiotemporal dynamics in climate change adaptation planning and emphasize regionally tailored public health strategies to mitigate cold related risks.