In 2021, the rainfall of Hengyang is 1421.7 mm, which is 6.2% more than the average (1339.1 mm) of the past several years, but the precipitation cab be categorized as a normal year.  But the distribution of rainfall in time and space is extremely uneven, and the anomaly changes of which is the most significant one in the three main factors --temperature, precipitation and sunshine (the factors used to evaluate the quality of climate). In January, March, May and September, the regional precipitation changes little, most within 50%. The months in which the rainfall is extremely lower than normal, significantly lower than normal, significantly higher than normal and extremely higher than normal in accounted for 9.2%, 24.2%, 6.7% and 18.3% respectively. In October, the precipitation is significantly lower than normal, which is 79.3% less than normal over the years.  And in this month, the precipitation of Hengyang is 4.7mm, which is the third lowest in the past 50 years. In December, the rainfall is abnormally high, for the average rainfall is 165.8mm, which is 304% more than the past several years and 244.2% more than last year at the same time. It is quite rare in history that rainfall in December is so abundant, and many measuring stations’ precipitations break the record of heavy monthly rainfall. On December 12th and 15th, there are two regional heavy rain  process, and because of which the measuring of 11 stations have reached heavy rain standard. During the rainy season (April to September) of 2010, the cumulative rainfall is 978.9 mm, accounting for 68.9% of the total annual precipitation, which is 16.7% more than the same period in history (838.8 mm). The average annual number of rainy days is 157.1 days, which is 3.5 days less than normal of the same period in history.