Prolonged seasons of compound heat–humidity extremes amplify vulnerable population exposure in eastern China

Compound heat–humidity extremes (CTHEs) pose escalating threats to human health, particularly for vulnerable populations (children and elderly) with limited physiological adaptability. This study reveals the expansion of CTHE-active seasons across eastern China from 1961 to 2022. Southern China (SC) and the Yangtze–Huaihe region (YH) exhibit earlier onsets and delayed terminations, prolonging hazardous CTHE seasons by one month post-2015 in SC. The prolonged CTHE-active seasons, coupled with population growth, have driven sharp increases in exposure across eastern China, with annual CTHE and hazardous CTHE exposure increasing by 106 million and 78 million person-days since the 2000s. Vulnerable groups constitute 39% of total exposure, with 11% (CTHEs) and 34% (hazardous CTHEs) attributable to season prolongation. Mechanistically, an intensified and westward-extended western North Pacific subtropical high enhances diabatic heating and moisture advection, driving prolonged CTHE-active seasons in SC and YH. Our findings quantify climate–demographic synergies in heat–health risks, providing a scientific basis for climate-resilient health strategies targeting age-sensitive populations in eastern China’s warming and humidifying hotspots. 温湿复合型热浪严重威胁儿童和老年人的健康安全.研究表明, 1961–2022年, 中国东部地区的温湿复合型热浪活跃季显著延长, 特别是在华南和江淮地区, 热浪开始时间提前且结束时间推迟.这种季节性延长直接导致了34%的危险型热浪脆弱人口暴露度增加.西北太平洋副热带高压增强西伸及其伴随的非绝热加热过程和水汽输送是造成热浪活跃季延长的关键驱动因素.该研究可为制定针对中国东部脆弱人群的热浪健康防护策略提供科学依据.