Areas around the Island of Montreal along the St-Lawrence and Ottawa rivers are already struggling with flooding after heavy rains earlier in the week and are bracing for more as the rains continue.
Montreal Mayor Denis Coderre on Wednesday asked people living on the tiny island suburb of Ile Mercier to leave their homes, a city spokeswoman said.
In Montreal, Quebec Public Security Minister Martin Coiteux said Friday that Canadian Forces personnel have been enlisted to help cope with the crisis in the province.
Both provinces have been dealing with fallout from heavy spring rainfall this week, and at least 124 Quebec municipalities were affected by flooding that inundated 1,326 residences, and forced the evacuation of 700 homes, according to Urgences Quebec.
Federal Public Safety Minister Ralph Goodale says the army will work with local authorities to coordinate relief efforts.
In Quebec, more than 1,500 homes are flooded and 340 roads affected by rising water levels.
The wet weather will take aim at Atlantic Canada starting Friday night and continue through the weekend.More news: Swansea still interested in Terry signing
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Prime Minister Justin Trudeau said that his government is "ready to do whatever we can to help people get through this".
The forecast, meantime, calls for up to 100 millimetres of rain this weekend in southwestern New Brunswick and between 25 and 50 millimetres in western Nova Scotia and parts of Labrador.
Environment Canada has forecast rainfall totally between 50 mm to 90 mm rainfall for the greater Toronto area through Saturday.
The same holds true for Toronto, which announced a contingency plan to close the heavily travelled Don Valley Parkway expressway if water levels in the adjacent Don River rise too high.
Emergency officials have been telling residents to stay away from the province's waterways and watch out for washed-out roads.
Several major rivers across the province had overflowed their banks as of Thursday afternoon.
Environment Canada has also issued a special weather statement for a large swath of southern B.C. due to the potential for severe thunderstorms, saying conditions are favourable for the development strong wind gusts, large hail and heavy rain.