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
Port of Murmansk Arkhangelsk and St. Petersburg (later renamed Petrograd). However, after the blocking of the Ottoman Empire's straits of the Bosphorus and Dardanelles to outside shipping and blockading of the Baltic Sea port of St. Petersburg, the Russian Empire could only use the northern port of Arkhangelsk. This port had limitations: when winter presented itself, navigation and shipping of any sort came to a halt. Therefore, it was decided to build a new port. The chosen location was in Murmansk due to its ability to accommodate sea traffic year-round, proximity to existing communities and relative ease to connect it to the empire's