Climate extremes revealed by Chinese historical documents over the middle and lower reaches of the Yangtze River in winter 1620

The snow-cover days over the middle and lower reaches of the Yangtze River (MLRYR) were extracted from Chinese historical documents for the winter of 1620, which includes the beginning of the tenth month of 1620 through the middle ten days of the second month of 1621 in Chinese lunar calendar. By using these records, the winter temperature anomalies compared with the 1961–1990 mean at nine stations were estimated. The results show an average of 50 snow-cover days over the MLRYR ranging from 30 d in Shanghai to 100 d in Jingzhou. The average snow-cover duration was approximately 70 d in Hefei, Huoshan, Nanjing, and Chaohu, and 40–60 d in Anqing, Wuhan, Changde, Changsha, and Jingdezhen. However, Shanghai and southern Jiangsu province had the lowest number of snow-cover days at 30 d. The regional mean winter temperature in 1620 was estimated to be 4.4 °C lower than the 1961–1990 mean. The maximum negative anomaly of −5.7 °C occurred in Jingdezhen, and the minimum anomaly of −3.6 °C was detected in Changsha. Both anomalies were significantly lower than those of the coldest winter during the instrumental observation period.