August 1931, torrential rains hit southern China, which caused the Yangtze River to flood killing nearly 3.7 million people. This was considered the worst natural disaster of the 20th century. Abnormal weather over central China began in the winter of late 1930. this was followed by a Spring thaw and heavy rains, raising river levels. The rains grew heavier in 1931 in a cyclone, thus causing the greatest flood in China.