Located in the north temperate monsoon climate zone, the basin has obvious continental climate characteristics, with long cold winter, hot and rainy summer, dry and windy spring, short autumn and large annual temperature difference. The average temperature for many years is between 5℃ and 3℃, the highest temperature is in July, and the daily average is 20 ~ 25℃, and the highest temperature can reach above 40℃. The lowest temperature is 5438+ 10 in June, the monthly average temperature is below -20℃, and the lowest temperature near Zhalantun in Nenjiang once reached -42.6℃. The average precipitation for many years is generally around 500mm, and the precipitation in the southeast mountainous area can reach 700 ~ 900 mm, while that in the western arid area is only 400 mm. The general trend is that the hilly area is large and the plain area is small. The southern and central parts are slightly larger, followed by the eastern part, and the western and northern parts are the smallest. The precipitation from June to September in flood season accounts for 60% ~ 80% of the whole year, and the precipitation from June to September in winter only accounts for about 5% of the whole year.

The historical flood years in Songhua River Basin are 1794, 185 1, 1856, 1862, 1886, 1896 and/kloc-respectively. 1929, 1932, 1934, 1943, 1945 *** 15 years. Among them, 1932 flood is the most extensive. The measured flood years after the founding of New China are 1953, 1956, 1957, 1960, 1969 and 1998 respectively. After the flood of 1998, the precipitation in Nenjiang River basin in the upper reaches of Songhua River was obviously too high, and three consecutive floods occurred. The first flood occurred from the end of June to the beginning of July, and the second flood occurred in? From the end of the month to the beginning of August, the third flood occurred in mid-August, which was a major flood in Nenjiang River Basin. Affected by the inflow of water from various tributaries, the water level in the main stream of Nenjiang River rose rapidly, and the highest water levels at Tuanjie, Qiqihar, Jiangqiao and Dalai hydrological stations respectively exceeded the historically measured highest water levels by 0.25 m, 0.69 m, 1.6 1 m and1.27m.. Under the condition of execution of the 6 th outlet of Nenjiang levee, the flood peak discharge of Qiqihar, Jiangqiao and Dalai stations all exceeded 1932. The highest water level 120.89m in Harbin, the main stream of Songhua River, was 0.84m higher than the historically measured highest water level, and the discharge 16600m3/s was the largest flood in the 20th century. There are two kinds of floods in Songhua River basin: one is caused by heavy rain in flood season; Secondly, there is continuous rainy weather in a certain area in the flood season, and the time can be as long as 1 month. In this continuous rainy day, heavy rain occurs and floods form. Floods in Songhua River basin include spring floods and summer floods. The flood time in spring flood season is basically the same as that in ice flood season in early spring, which occurs in April-May every year. Ice dams often appear in glacial floods. According to the statistics of Yilan Station, ice dams occurred in 13 years from 1956 to 1976. The height of ice dam is generally 4 ~ 6m, the highest is 15m, and the length is 5 ~ 10km. Floods in summer and autumn occur in June-August, sometimes postponed to September.