Situated on the eastern rim of Eurasia and abutting the Pacific Ocean, the basin is subject to the combined effects of monsoon climate conditions, oceanic currents, and mountains that direct air circulation patterns. The eastern Amur-Heilong basin has a humid monsoon temperate climate and is an area where monsoons reach their northernmost latitude on earth. The western basin (upper reach of the Amur-Heilong River ) is sheltered from monsoon influence by mountains and is arid.
Mean annual temperature varies from -7В° C in the north to +6В° C in the south of Amur River Basin. Annual precipitation varies from bare 250 mm in the westernmost Argun River watershed in Dauria to well over 800 mm in Lower Amur and Ussury River valley.(see map)
Nearly two thirds of the basin's precipitation falls in the three months from June to August. May and September are transitional months and the dry season extends for seven months, from October until April during which precipitation is only 15% of the annual total. Floods occur annually during the short three-month wet season, a period during which 84% of the big storms occur. Even so, water is in short supply throughout most of the basin during the much longer dry season and droughts are especially long and severe in south-western part of the basin.
Floods are one of the most important natural processes and determine, in part, the diversity and productivity of the Amur-Heilong ecosystems. The shaping and dynamics of the vast floodplain wetlands, the major nutrient cycles, and the life-cycles of all aquatic flora and fauna depend primarily on the periodicity, volume, and other characteristics of floods.
Population dynamics and migration patterns of many species are closely linked to flood and drought cycles, as demonstrated for stork, cranes, bustard, and even musk deer.

Global climate change is quite obvious, especially in western part of the basin during last 100 years. Temperatures in the eastern Amur-Heilong basin have risen 0.60C , while, in the central and western basins, increases have reached +1.70C at Blagoveshensk and even more in Chitinskaya Province. Ecosystems in the basin are vulnerable to any abrupt changes and are already actively evolving in response to modified climate patterns. Human activities are also changing in response to natural shifts.