Using observational datasets and statistically downscaled CMIP6 model simulations,this study identifies cluster high-temperature events in the Yangtze River valley and examines their historical evolution and future projections.Results indicate significant increasing trends in the frequency,duration,cumulative intensity,and maximum influential area of such events from 1961 to 2021.Under both SSP2-4.5 and SSP5-8.5,the duration,cumulative intensity,and maximum influential area of cluster high-temperature events are projected to continue strengthening throughout the 21st century,with more pronounced increases under SSP5-8.5.By the late 21st century,the largest enhancements are expected to occur in the lower reaches of the Yangtze River valley,followed by Chongqing and the Sichuan Basin.The frequency of cluster high-temperature events shows a substantial rise until the 2050s,after which the trend moderates under SSP2-4.5 and reverses to a decline under SSP5-8.5.By the century's end,the greatest frequency increases under SSP2-4.5 are projected in Henan and Hubei,followed by Anhui,Jiangxi,Chongqing,and the Sichuan Basin;under SSP5-8.5,the strongest increases occur in the Sichuan Basin.Furthermore,cluster high-temperature events are projected to begin earlier and end later in the year,indicating an extended seasonal duration under both scenarios.In response to these changes,the affected population in the Yangtze River valley is projected to increase and peak around the 2050s.Population exposure to event intensity is also expected to rise steadily throughout the century,with larger increases in urban areas than in rural areas—particularly under SSP5-8.5.