The Saimaa Canal, one of Finland's primary waterways, was due to open to boats and ferries after the winter season on Monday afternoon.
Officials warn boaters on the 814-kilometre channel to be aware of increased traffic.
The icebreaker Protector will clear a route into Puumala on Monday evening, continuing on to Vuohisaari harbor and Inkilänniemi in Savonlinna by Tuesday morning. Protector will next arrive in Joensuu around 3 pm on Tuesday, followed by the Puhos harbor on Wednesday.
To the east in Karelia another vessel, Meteor, will clear routes into the Pulp and Honkalahti docks in Joutseno and the Vuoksi harbor in Imatra. Meteor will push on toward Varkaus, arriving there on Tuesday between 4 pm and 6 pm.
The icebreaker will reach Kuopio by midnight Tuesday and Siilinjärvi harbor by Wednesday, 1 April.
The timetables may be affected by assistance operations and variations in ice cover.