Lake Onega is relatively cold, with temperatures below for half of the year and average summer temperatures of about . The catchment area of drains into the lake via 58 rivers and more than 110 tributaries, including the Shuya, Suna, Vodla, Vytegra and Andoma. The only outgoing River Svir, which marks the southern boundary of Karelia, runs from the southwestern shore of Lake Onega to Lake Ladoga and continues as the Neva River to the Gulf of Finland. The White Sea–Baltic Canal runs through the lake from the White Sea to the Baltic Sea. The Volga–Baltic Waterway connects Onega Lake with the
Arkhangelsk evidence of a stronger case of Russian colonization than previously thought. In the 12th century, the Novgorodians established the Archangel Michael Monastery (named after Michael the Archangel) in the estuary of the Northern Dvina River. The main trade center of the area at that time was Kholmogory, located southeast of Arkhangelsk, up the Dvina River, about downstream from where the Pinega River flows into the Dvina. Written sources indicate that Kholmogory existed early in the 12th century, but there is no archeological material to illuminate the early history of the town. It is not known whether the origin of this