A record-breaking extreme heat event caused unprecedented warming of lakes in China.

Strong evidence confirms that extreme climatic events,such as heat waves,storms and droughts,are becoming more frequent due to anthropogenic climate change[1].These extreme events may have overwhelmingly negative impacts on lake ecosystems[2].Specifically,by warming lake surface waters,extreme heat events are expected to influence many within-lake physical,chemical and biological processes[3].Critically,extreme heat events can alter the lake environment in only a fraction of the time that is needed for achieving the same effect of long-term climate change[4].In some cases,extreme heat events can exceed the resilience capacity of a lake ecosystem and lead to a loss of functionality and can even trigger catastrophic regime shifts[5].From mid-June to late August 2022,a record-breaking extreme heat event,with the longest duration and highest intensity since recording began in 1961,swept across China[6].The direct driver of this heat event was the Western Pacific Subtropical High,which normally sits as a smaller pressure system to the east of Yangtze River Basin.How-ever,in summer 2022,the system was strong and hovered over Yangtze River Basin,thereby preventing cold air from the north and moisture from the Indian Ocean from reaching the region[6].Here,we used satellite observations from 2000 to 2022 to demonstrate the effects of the unprecedented warming of China's lakes caused by this extreme event.