利用1961 -2022年全国664个地面观测站的逐日最高气温资料， 系统分析了全国和各分区极端高温事件及其起讫日期的时空分布及演变特征。结果表明， 我国有近9成极端高温事件集中在夏季， 其中出现在7月的极端高温事件占全年总数的39.3%。全国极端高温事件在近62年迅速增加， 极端高温日数和高温极值在9成以上的站点监测到增加趋势。极端高温事件在高海拔地区的增加更为明显， 青藏地区的极端高温日数每10年增加2.9天， 高温极值增幅为0.34 ℃·（10a）^-1。极端高温事件开始日期和结束日期在全国大部分站点分别呈现出明显的提前和推迟趋势， 受起讫日期的反向变化影响， 极端高温事件持续期的增加趋势更为突出。西南地区是各分区中极端高温事件持续期增加最快的地区， 其增加速度达10.8 d·（10a）^-1。长时间维持的连续性极端高温过程对人民生产生活造成严重威胁， 进入21世纪以来， 连续性极端高温过程在我国呈现出高发态势。华南和西南地区的连续性极端高温过程的增加较为明显， 其中华南地区的连续性极端高温过程频次和累积日数每10年分别增加0.5次和2.5天， 均为各分区中最高。

Using the daily maximum temperature datasets from 664 observational stations during the period of 1961-2022， this paper systematically analyzed the spatio-temporal distribution and variations of the extreme heat events as well as their start and end dates.The results showed that nearly 90% of the extreme heat events in China occurred in summer， of which 39.3% occurred in July.The extreme heat events increased significantly in the past 62 years in China， characterized by increasing days and maximum temperature of extreme heat events at over 90% of the stations.The average days and maximum temperature of extreme heat events increased by 2.1 d and 0.18 ℃ every 10 years in China， respectively.The increase of extreme heat events was more obvious in high altitude areas， with more than 90% stations showing a significant increasing trend in extreme heat days， and more than 87% stations showing a significant increasing trend in maximum temperature in Qinghai-Tibetan Plateau.The increasing trends of days and maximum temperature were up to 2.9 d·（10a）^-1 and 0.34 ℃·（10a）^-1 in Qinghai-Tibetan Plateau， respectively.The start and end dates of extreme heat events showed obvious advance and delay trend in most stations in China.The duration of extreme heat events increased more distinctly due to the reverse variations of the start and end dates， characterized by increasing duration of extreme heat events at over 90% of the stations in all regions.Southwest China was characterized by the fastest growth of extreme heat events in all regions， with the largest rate of 10.8 d·（10a）^-1.Persistent extreme heat events maintained for a long time posed a serious threat to people’s production and life， which occurred frequently in 21 century.Similar to the variation of extreme heat events， the persistent extreme heat events also showed a significant increasing trend in most stations in China.The persistent extreme heat events increased rapidly in South China and Southwest China.Specifically， the largest increase was observed in South China， with the trends up to 0.5 times·（10a）^-1 and 2.5 d·（10a）^-1， respectively.In addition， the increase of persistent extreme heat events was also obvious in Qinghai-Tibetan Plateau， with trends of frequencies and accumulated days up to 0.3 times·（10a）^-1 and 2.1 d·（10a）^-1， respectively.