cartographic program by the Jesuits Jean-Baptiste Régis, Pierre Jartoux, and Xavier Ehrenbert Fridelli, who found it a stronghold, serving as the base of Manchus controlling the Amur River basin. The Aigun Treaty was concluded at Aigun in 1858. According to this treaty, the left bank of the Amur River was conceded to Czarist Russia. After the Xinhai Revolution, Aigun became the county seat of the newly created Aigun County by the Republic of China. On November 15, 1980, Heihe City was established, administering two county-level cities and three counties including Beian, Wudalianchi, Nenjiang, Sunwu and Sunke. Aihui County was abolished, being merged into the Heihe City. Geography Heihe is located at the South bank of the Amur, opposite to the city of Blagoveshchensk in Russia's Amur Oblast. Its jurisdictional area stretches for , which spans from 124° 45' to 129° 18' E longitude and 47° 42' to 51° 03' N latitude. Domestically, Heihe City borders Da Hinggan Ling Prefecture to the north, Yichun to the southeast, Suihua to the south, Qiqihar to the southwest, and Hulunbuir (Inner Mongolia) to the west. The Amur has formed the Sino-Russian border since the 1858 Aigun Treaty and 1860 Treaty of Peking. The area north of the Amur had previously belonged to Imperial China. Climate Heihe experiences a monsoon-influenced humid continental climate (Köppen climate classification Dwb), but Dwa in the south of the prefecture, with long, bitterly cold, windy, but dry winters due to the influence of the Siberian high, and warm, wet summers, due to the East Asian monsoon. Based on data from 1981 to 2010, the monthly daily mean temperature in January, the coldest month, is , and July, the warmest month, averages , with an average annual temperature . Close to two-thirds of the annual precipitation falls in the months of June to August. Extreme temperatures have ranged from to . Administrative divisions Transportation The transportation to and from Heihe is as follows: Highways China National Highway 202: Heihe–Dalian via Harbin, Jilin City and Shenyang Provincial highways: Heihe–Mohe, etc. Blagoveshchensk–Heihe Bridge, completed at the end of 2019, is a 2-lane highway bridge over the Amur to link Blagoveshchensk and Heihe. Railway (China Railway): Heihe–Bei'an to Harbin, Qiqihar and Daqing Air: Heihe Aihui Airport The world's first international cable car to Blagoveshchensk has also been proposed to open in 2022. Energy West of Heihe, there is an HVDC back-to-back station for realizing